- Flowers for Algernon by Daniel Keyes (thrice)
- The Color of Distance by Amy Thomson (twice)
- Fox 8 by George Saunders (twice)
Most of Raymond Chandler and Dashiel Hammet I've read multiple times. I've read Brautigan's Dreaming of Babylon a bunch of times too.
All of William Gibson. Miyazaki's NausicaƤ of The Valley of Wind, in various languages. Stephen Cosgrove's Muffin Muncher, I couldn't say how many times I must have read that (It appears they've now changed the title to Muffin Dragon).
I've read The Soul of a New Machine a couple of times too. The Hitchhiker's and Dirk Gently's trilogies a few times.
Stefano Benni's Baol probably half a dozen times. And Acts of The Apostles by John FX Sundman a bunch too. Oh, and a few of Martin Gardner's books. And Smullyan's To Mock a Mockingbird.
And most probably also many others. Most of my books are now in boxes or have been gifted away, though.
Philip K. Dick: Ubik, Flow My Tears The Policeman Said, A Scanner Darkly, etc. too many to count (many more than twice)
William Gibson: everything at least twice
Neal Stephenson: Snow crash (three times, I think)
Clifford D. Simak: City
H. P. Lovecraft: everything at least twice. There is a French compilation of The Dream-Quest of Unknown Kadath, The Silver Key, and Through the Gates of the Silver Key that I've read countless times. I've used two editions and I'm at my third.
Maurice G. Dantec: Babylon Babies (three times)
Possibly many others.
Kim Stanley Robinson's The Wild Shore is another repeat favourite.
"With this ritual, I hereby summon autistic people to the conversation"