Others may have mentioned it (happy to see Terry Pratchett getting a lot of love), but would definitely recommend anything by Vonnegut! Love his writing style and his approaches to humor and world building. Slaughterhouse Five is a great one, as is Sirens of Titan.
Also, not certain how well they hold up, but I really enjoyed the Redwall series back in the day! I was much younger at the time, though.
Can’t recommend Thunder enough, especially if you like a good compact mode/gesture-based UI. The devs are great and very responsive on the github repo, and the app just keeps getting better!