There is a lot of good and bad scholarship on the Holocaust. Anyone that takes a real interest in should read the important firsthand accounts that are the basis for the best scholarship (outside of hard data/records from govt and institutional archives).
Two offhand:
Jankiel Wiernik “A Year in Treblinka”
written in Polish 1944 when he was fresh from escaping during the uprising and one of the very few legit Treblinka survivors that could give account of what went on in an actual extermination camp. In 1966 Steiner took Wiernik’s account and added bad scholarship and his own BS. Avoid Stiener’s Treblinka book, read the straight report by Wiernik. Accounts of the extermination camps are very hard to come by because they really did murder 99% of the people brought to them within 24 hours, unlike the "work camps" that have a large number of firsthand survivor accounts.
Captain Witold Pilecki (a The Auschwitz Volunteer) a Polish Intelligence officer who volunteered to use false papers to be arrested so he could give a firsthand report on what was happening in Auschwitz in 1942. It’s a “non-Jewish” eye witness account, which is rare and valuable since some try to infer accounts by Jewish victims are suspect or biased.
My grandfather helped liberate Buchenwald and later spent months guarding minor SS figures and soldiers being tried for war crimes so I took an early interest in WW2 as a kid/teen. As I got older I managed to separate a lot of the wheat from the chafe, by checking the references/source notes in the back of most books. They always referred back to a handful of reliable firsthand, period sources and I feel those should be what’s read.
I’d also recommend The Holocaust Industry by Finkelstein if your curious how Israeli political aims have tried to corrupt the historical record for money and propaganda purposes which has done great favors for Holocaust deniers.
Reading German or Polish is usually a must for Holocaust/WW2 researchers. For awhile Russian was very valuable for that brief window the Soviet archives were made available to researchers, it was like an entire new universe was opened in the 1990’s when the west could finally read about the Eastern front from firsthand Soviet accounts and archives.