@Konigsberg Eh i am alright it is just my grandmother being sick.
so PHB, DMG(both 1st edition and second edition because the 1st DMG is the best shit there is) and MM is a must.
Arms and Equipment guide is really good for visual references and more explanation of various weapons, armors, clothing etc. Aurora' Whole Realms Catalog adds interesting non mgical but fantastic equipments, clothes, gadgets etc. It i a forgotten realms accesory but impressively useful. Also adds many interesting mundane items as well.
Tome of Magic adds Wild magic, and more spells, options, eplanations on Priestly magic and arcane magic and put out how different they are and their limitations. Encyclopedia Magica is 4 volumes of magical items from all ad&d editions, settings etc. with random generation tables, rules on items etc. wizard spell compendium is all wizard spells, with tables for learning random spells, all rules for magic, tables and references to spells from their rarity, to school, to race etc. It is a hobbily designed book (wrong in many places, edit is horrible etc) but is useful because as far as i know it has ALL WİZARD SPELLS in it. Priest's spell compendium is also same. Both have prapered spells for x type of creature, more indepth analysis on liches, vempires etc so there is also that. Book of Artifacts is a bit better book. it gives us artifacts, also rules on how to create artifacts, and also rules on how to create potions, magical items etc. (they are good). Al these books are very useful but hastily created in my opinion.
Castle guide is for entry to base building, taxing, armies etc. Of ships and sea is same but for sea life. Very very useful but also very optional as in your campaign you might never use it. City Sites, Castle sites, County sites give you locations, interesting landmarks etc for you campaign so you might diversifiy the towns, cities and villages. they are very fun and useful to have.
Book of series if very good in general.
Complete book of Dwarves is the best book written for dwarves until ACKS's by this axe. it is still one of the best books written for any game. Has good rules class options, equipment for dwarves, a very good explanation of dwarven society, physiology etc. This book has balls, and i could write 20 volumes of praise for its first chapter only to end it with the next chapter is better. It is manly, it is virtuous it is divine.
Complete book of Gnomes and Halflings wishes it was as good as dwarves, it is still good, still useful.
Complete book of elves is something that would not have existed if we had a good world. It is the antithesis of Book of Dwarves. All the lore is like, elves are superior, elves never got drunk on dwarven ale but then a dwarf drinks elvish wine he could not endure the horrible alcohol of other races. Elves can do orgy and gain +5 to attack roles and ac because they are that good. But i believe the class options are not as OP as people suggests, some spells, equipment etc is not bad. remove the lore, and keep them i say(actually you do not need to remove the lore either i believe there was an elven space armada in the spelljammer universe that tries to kill and destroy all who learned that elves actually bringed their world to a nucleer apocalypse and had to escape to all other universes and start larping as nature loving hippies even though they are actually the multiverses first nature killers LOL)
Book of Humanoids adds humanoid options from Goblin to Pixie. Tiny races, small races Lare races, Huge races that can fly, burrow, etc. Most of them are suboptimal because mst of them are uncivilized (as in not having much relationship with other races aside from murder and rape) but it also adds rules on how to bring one to a party, how would society react to the new race etc they are retty good rules i believe. never had to use it because people never wanted to be a humanoid.
Complete class books are mostly class specific like the name implies. most of them do not require a reading if you do not have a player playing that said specific class but some of them must be read in my opinion regardess of players. All of the race and class books add kits (variants of the classes) and roleplaying options.
Complete barbarians handbook:
Adds Barbarian and Shaman classes, rolaplay options, kits, equipment etc. Solid book but very few juicy parts.
Bards:
It is a very good book to learn about art in general. Gives you a very wide list of musical insturments, poetry types, music types speed accent of music etc lol. Useful explanations of magic, bard specific items and spells, performance rules ( gaining xp and gold from performances) reputation system etc. Also adds bards for other races (only humans and half elves can be bards but with this book there are bard equivelant classes for every other race)
Druid:
Adds agriculture rules and also herbal magic. other than that it is very druid focused so if you are not going to focus it then pass.
It also adds druid organizations and how they work, sacred groves and how to make one for your campaign etc.
Fighters handbook:
Amazing book. adds more in depth fighting rules, options to all classes (Shield bashing, Expertise, Weapon mastery) adds many rules for piecemail armors (same with dark sun and allows you to customize your armor by waight and its ability to protect.) adds many good roleplaying options and campaign options for no magic play etc. Adds weapo smithing and armor smithing rules. Only second to book of dwarves.
Ninja
Lol this book is very anime. it has glorious kung fu rules (allows you to create your own martial arts) rules for ninjas ki shit etc. If you are like me and want to add martial rules, use it. otherwise burry it and never speak of it.
Paladin:
It is a very solid book because it adds many organizations, more in depthn look at how to play lawful good, nice magical items, holy swords and most importantly knight orders. I like this book very much.
Priest:
A must for all games. Actually does not give any new spells or magical equipments unlike many other books but gives us how faith workds, how gods work, what are the duties of priests, hw to create your own religion etc. a nice book for worldbuilding and therefore a must.
Psionic:
there are two different rules for psionics so i am going to pass discussing it for now.
Rangers:
I mean, it gives very good ranger lore, role play tips, options equipment. Other than that i would still recommend this for general reading because it also gives good proficiencies (skills for ad&d) for survival and travel like crude weapons etc. they are fun to use.
Thieves:
Gives us many mundane items that rocks. need to sneak but there are dogs, ok here is a catstink and dog pepper. a very very impressive book. second ony to the book of dwarves. me and my friends yearn for an all thief play because of this book. This is the most impressive class book ever.
Wizard:
Goes indepth into schools, how a conjurer work, how a necromencer feels etc. Great rules on magic (how certain spells work un underwater, how magical items are created, how wizards fight) gives us commentary about how wizards see eachother (cınjurers believe they are best while illusionists seen as weaklings, idiots etc) How to create your own spells, spell research, building libraries, labs etc. gives us new spells of course. very very good book overall. Also gives us very interesting story hooks ike spells that have never been created, or ideas for useful items.
Necromencers:
very solid book. explain necromancy, how to implement good or neutral necromancers, which necromancy spells count as evil and why, arguments counter arguments, options for cleric necromancers and wizard ones. new spells and options. rules for madness (as in a mad necromancer) and corruption.
Book of villians:
very good book on how to build villians and organizations and how to design adventures/ campaigns revolve around them. an underrated book.
Legends&Lore, Monster Mythology, Faiths and Avatars etc all of them about various gods and their faithful, clergy etc. useful.
collage of wizardry, , sloppy, shitty but salvagable adventures about how to dm a campaign revolve around a single class adventure. Collage of wizardry has rules on how to level up even though you are not gaining xp and just study as a mage (it takes years and years no wonder wizards are old.)
Den of thieves is good to look at thieves guilds and how to operate them. a must for thief characters of course. Bastion of faith is for temples. the latter two is better but i will gave a better alternative for collage.
There are various guidebooks for worldbuilding, adventure building and dungeon building. they might be useful but eh, we live in an era of internet and you are not a newbie. going to skip.
Historical reference books are kino, but mostly useless for fantasy. They gave us lives from vikings, romans, kelts. classes, kits, rules, options for playing that historical era. very much salvagable for your own world.
Monsteres arcana: there are 3 sets of them. all is made up of one codex for a monster type, 3 adventures from mid level to high level. They are mind flayer, beholder and the shark race i forgot. Dm'ed the mind flayer one. it starts slow but holly, the last part is kino. all 3 lore books are great. they are a must even if you will never use them. Beholder one was so good that i stopped my campaign to run a beholder dungeon.
Setting books:
All settings came with optional rules, setting monsters, races and classes. You can look all of the setting monster manuals. they are very good. generic monster manuals have mixed monsters but setting specific ones focus on a specific type of idea. Oriental, Horror etc.
If a settig seems interesting to you, read all of it but here are some settings and what they can add to your custom world(rules, classes, races.)
Al-Qadim: interesting world building but other than the Sha'ir class, i cannot fathom anything i can recommend from here. Of course i am not saying Sha'ir is a good class. it is fun on paper. Basically it has a genie that helps him steal spells from others. you can steal priest and wizard spells. the higher level the spell is the less likely you are going to steal it. the more levels you have the more successful you are going to steal a spell. that is basically it. and of course the genie is not your slave but a partner so keep it happy.
setting has very nice aesthetics and vibes is nice. Setting is heavy middle east, and a orientaist one at that. Magical baghdat, jinnies, civil gnolls, gold and silk, veiled women, eunch haremguards with curved blades etc.
Birthright: one of my favorites. Has rules on domain ruling, proficiencies for politics and warfare, realm magic (magicusing leylines and took months for great effect) war magic (use your spel slots but with assiatance and prep time so your magic missle is not hitting 1-5 people and dmg them but effect a whole unit of 200 probebly killing 100 of them). army rules etc. it is very kino! also had guilder class. a rogue class that is all about mercentalism. It also adds magician class. it is a lesser mage basically only good for divination and illusion magic and bad at everything else. In BR unless you have elven or divine blood in you you do not have any magical aptitude and therefore you are a magician.
Has its own naval rules. has its own cultures, has its own drawf, halfling and elf races (different than core phb) has different understanding of monsters. (ther than undead, elementals, goblins orcs etc and fey,) most of the monsters are myhtic. there are no liches, but A LICH, A VAMPİRE, A MINATOUR A GARGOYLE with its own history, advesaries and curse. has a shadow realm(halflings are connected to it, it is different from 5e one and specific to this setting.) the last books were not printed so sadly it is half complete but still great!
Has 6 human cultures (one is extint greek, others are british, german, rus, celtic, arabic).
Book of magecraft is a better collage of wizardry. has explanations for which races and cultures look at which schools of magic in which way and also their general opinions on magic. how people study magic, templates for schools of magic, which buildings it must has, rules on apprenticeship (how many hours does an apprentice needs to be tutored, what are the responsibilities etc.) MYTHIC FAMILIARS AND HOW TO FIND THEM!
Dark sun: Half-dwarf, thri-kreen, half-giant, different dwarves, elves and halflings. druid, ranger, thief, bard, fighter,cleric works differently. fighter is more of a general and tactician. we do not have any gods but elementals and sorcerer kings. we have psionics, we have templars (paladins but are not good, and their powers are being a shittier cleric that is allowed to rape, imprison, judge, execute, steal lol) gladiator (fighters that are better at fighting then fighters at fighting). we have traders (similar to guilders but more assasination and less guilding) wizards also work differently. magic consumes life force and we have preservers (normal wizard class that does not destroy) and defielers (wizards but levels up faster therefore stronger, but evil). Hardcore monsters, interesting proficiencies (bargaining is kino water finding etc is efficient.) rules on how a lawful good would behave under stressful situations rules on equipment made from sub par materials (bones, stone obsidian etc) rules on piecemail armor (chest has bone plate, right arm is leather, left arm is chainmail, lefs are empty how much ac do i have?)
The complate gladiators handbook adds rules on gladiator fights, sample arenas, new weapons (fun and silly) rules on bleeding and called shots, new rules for fake fighting, new proficiencies (oil massages) bombs, poisons and many other stuff.
The will and the way: new psionic options.
Dark sun revised setting book: massacred the lore but kino races, options and rules. there is a new psionic ruleset and i prefer this ones over the one in psionic handbook. this versions ruleset is also in player options books as well. going to talk about it in there.
Dragonlance: I believe it is overhated and underestimated by most d&d players. interesting raceplay, interesting rules on magic. adds fake priest mages, fake healing spells, alignment and social class restricted options. many humanoid races and kenders.
Greyhawk: still the default setting, other than adding fortune tables, zodiac tables etc for its own setting, does not affect much. still the books are very helpful to develop your own cities because who would have guest the city of greyhawk would have such presence in the setting

The scarlet brotherhood adds monk class (player options and priests handbook has rules on unarmored combat, ninjas has rules on martial arts and all have a monk class but i believe this one here is the best monk this edition has.)
Ravenloft: adds gothic races and horror and madness options, options on paladins and good alignments as well as evil ones. domains of drad has new class options, champions of the mists adds eremite class (alchemist wizard with a touch of druid. very interesting class) there are also otherclasses as well but i only remember this one.
Masque of the red dead: it is out world but 19th century. wanna play steampunk, dieselpunk ww1, cthulhu but lazy to leanr another system? occult adventures, polish, muslims, chinese, british, indians? want to go to a school, want to use trench fighting rules, fire arms, trains, and want a universe where you can buy lands and a sheep herd for only 10 cents?? want non magical healing rules, cars, Penny Dreadful adventures?? this is the shit.
Planescape torment is planescape torment. it has too much stuff it but unless you are going to start there, i would like to skip it for now.
Spelljammer: nice raaces, nice kits but is mostly has spelljammer rules. unless you want to go into space, skip it it is not mandatory.
forgotten realms: i recomended some of the stuff in it.
Player options:
Combat and tactics: changes the weapon dmg dies, adds new options to weapons, new weapons, crit rules, new combat rules on flanking, AoO clarification on rules, new crit system, new wrestling and pummeling system, I never really used all of it but i believe it is the best one out of the others. still not good. at this point the cmpany was at the brink of collapse.
Skills and powers: worst one i believe. here have 12 stats instead of 6, here have class points to customize your class. my fighter cannot wield axes and can only wear high armor and now it has d12 as HD, spent 10 points in your half orc race to get infravision but also gain 5 points from ugly ass mug penalty, have traits etc. i dislike them BUT this book also had new kits, new proficiencies and they are not bad. It also had the same psionic rules from Dark Sun revised.
Basically psionics works in two different ruleset.
one uses stat rolls other uses a new combat system.
both has psionic points. in the first one you spend a required amont of points, then roll required stat (str, dex, con etc) with given modification (-6 to 0 i believe.) if the roll is successful, you did it.
in the new system every creature has MThac0 and MAC for mental attack rolls and mental defence. first of all you have mental attack types, (attacking id, psycic whip etc) if the opponent is not psycic, use one of the attack types to attack the mind once, now his mind is defenceless to your attacks. use a power against him by spending a mthac0 roll against his MAC. if successful it happens.
if the opponent is also psycic, to open his mind to your powers you need to melt his psycic points. choose an attack mode and attack. the opponent also choose a defence mode, some attacks workd better at some defences, some work worse. if you erase your opponents points to 0, you can attack his mac like it was a non psionic person. of course psionics have better MAC and MThac0 but high int, wis, con etc effects MAC as well. I prefer this version of psionic powers ruleset.
it adds new schools of magic as well i do not hate them.
Spells and magic: not a bad book, less problematic then the previous one and also maybe more usefull then both. updated spel list, more explanations on how spells work, rules for spell creation, options for semicasters (paladin, bard etc) options for multiclass characters, new rules for slot based casting, new proficiencies, new equipments, new methods of casting instead of vancian casting channel magic etc.