I thought these were all very good.
Traveller, The Dark River, and The Golden City, by John Twelve Hawks
Daemon, Freedom, and Kill Decision, by Suarez
Confederacy of Dunces by Toole
Alas, Babylon by Frank
Gates of Fire by Pressfield
1984 and Animal Farm, by Orwell
Brave New World by Huxley
Atlas Shrugged by Rand
The Lord Of The Rings trilogy, and The Hobbit, by Tolkien
All Quiet On The Western Front by Remarque
Dune by Herbert
Starship Troopers by Heinlein
All of the books in the Ender's Game universe, by Card
For Whom The Bell Tolls by Hemingway
Cryptonomicon and Anathema, by Stevenson
A Song of Fire And Ice/Game of Thrones by Martin
The Foundation series, by Asimov