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