Dune by Frank HerbertRead about the other entries on the list.
The premise of the first novel in Herbert's famous cycle of stories about humanity's distant, galaxy-spanning future is that humans have abandoned technology after a horrific apocalypse involving AI. In its place, they have medieval-style "guilds" of witches, pilots, and other groups who have been genetically altered by the spice melange to do jobs that computers once did. The humans in the books have a very spiritual relationship to both the spice and the ways they are transformed by it. Though they are clearly operating in a technological world of spaceships and intelligence explosions, most characters view themselves as part of a mystical system.
Dune is among Robin Sloan's five science fiction books that matter, Mohsin Hamid's six favorite books, io9's best and worst childbirth scenes in sci-fi & fantasy and top ten science fiction novels you pretend to have read, and on John Mullan's lists of ten of the best vendettas in literature and ten of the best deserts in literature.