Terry Pratchett, I ended up memorizing my library card number from the sheer number of reservations I made just to read the entirety of the Discworld series. Hell, I even did inter-state library borrowing (back in the 90's) to be able to read all of them.
Anne McCaffrey, for all that she's damn near cancelled nowadays, I still have a warm feeling for. And a signed book.
Diana Wynne Jones is another I loved. Dark Lord of Derkholm and Deep Secret are two of my favorites.
I'm kind of surprised he's still hanging in there, but I'll miss Alan Dean Foster when he goes. Dear god has he written a number of series and single books I liked. Spellsinger series, the Flinx series, "Quozl" was a weird one, as was "To The Vanishing Point".