I tried to do this and found that I can't really compare fiction and non-fiction. So, I made two lists.
Fiction:
- George Orwell - 1984
- Ernest Hemingway - "The Snows of Kiliminjaro" (short story)
- Charles Dickens - Great Expectations
- Lewis Carroll - Alice's Adventures in Wonderland
- Ray Bradbury - Fahrenheit 451
- Joseph Heller - Catch-22
- J. R. R. Tolkien - The Lord of the Rings
- Richard Adams - Watership Down
- Anthony Burgess - A Clockwork Orange
- Ken Kesey - One Flew Over the Cuckoo's Nest
Those are the first ten works of fiction I'd recommend to a friend looking for something to read. I find them all both profound and entertaining. It hurt me to omit my all-time favourite writer, P. G. Wodehouse, but he doesn't have one definitive work.
Non-fiction:
- Viktor Frankl - Man's Search for Meaning
- Richard P. Feynman - Surely You're Joking, Mr. Feynman!
- Douglas R. Hofstadter - Gödel, Escher, Bach: an Eternal Golden Braid
- Plato - The Republic
- The Bible
- The Quran
- Charles Darwin - On the Origin of Species
- Friedrich Nietzsche - Beyond Good and Evil
- Henry David Thoreau - Walden
- Truman Capote - In Cold Blood
The five in the middle are books I've read that I think deserve to be read by everybody, and the other five are personal favourites. A couple of them check both boxes.