J.R.R. Tolkien: The lord of the Rings (lost count)

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.