Many of Philip K. Dick books and short stories, but Ubik and A Maze of Death are my favorites.

William Gibson's Sprawl trilogy (Neuromancer, Count Zero and Mona Lisa Overdrive)

Douglas N. Adams - The Hitchhiker's Guide to the Galaxy

Frank Herbert's Dune books

Theodore Sturgeon's More Than Human

Robert A. Heinlein - Citizen of the Galaxy

Robert Charles Wilson's Spin trilogy

Frederik Pohl's Heechee books