Calvin and Hobbes, by Bill Watterson

The Culture series, by Iain M. Banks

The Earthsea series, by Ursula K. Le Guin

The Ender Quintet, by Orson Scott Card

The Hitchhiker's Guide to the Galaxy series, by Douglas Adams

The Alliance-Union universe, by C. J. Cherryh

The Dirk Gently series, by Douglas Adams

The Wizardry series, by Rick Cook

• Animal Farm, by George Orwell
• Brave New World, by Aldous Huxley
• The Coldfire trilogy, by C. S. Friedman
• A Connecticut Yankee in King Arthur's Court, by Mark Twain
• The Lord of the Rings trilogy, by J. R. R. Tolkien
• Temporary Duty Assignment (and its prequel Nice) by A. E. Ash
• Watership Down, by Richard Adams

Books in this list might very well get moved to one of the three tiers above. But first I need to re-read them, since I've generally only read each of them once, and that one time was quite a while ago. As such, I neither remember clearly what I thought after reading them, nor did I have a very good foundation for critique at that younger age to really make any definite determinations of their worth to me. But to be on this list, I at least need to have a strong suspicion that a second reading would be valuable, reflecting the worth that the books likely hold for me.

• A Wrinkle in Time, by Madeleine, L'Engle
• Slaughterhouse-Five, by Kurt Vonnegut
• Welcome to the Monkey House, by Kurt Vonnegut
• 1984, by George Orwell
• Dune, Dune Messiah, and Children of Dune, by Frank Herbert