
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.
Frederik Pohl (Gateway, the Space Merchants)
Ursula K. Le Guin (The Dispossessed, Left Hand of Darkness)
Iain M. Banks (Culture novels)
You will find many Sci-Fi treasures by just going through http://en.wikipedia.org/wiki/SF_Masterworks
Tractatus Logico-Philosophicus
(Ludwig Wittgenstein)
Being and Time (Martin Heidegger)
Of Grammatology (Jacques Derrida)
Writing and Difference (Jacques Derrida)
Martian Timeslip (Philip K. Dick)
Ringworld (Larry Niven)
The Forever War (Joe Haldeman)
The Metamorphosis (Franz Kafka)
Finally, the Greek tragedies and Goethe's poetry are basically perfect.