As far as non-fiction goes, and for supercharged brain fuel: Anything by Mortimer J. Adler, but especially "How to Think About God: A Guide for the 20th-Century Pagan"; "Six Great Ideas"; or "The Idea of Freedom: A Dialectical Examination of the Controversies about Freedom".
For fiction, the classics are still good: "Finnegan's Wake" by James Joyce; "The Catcher in the Rye" by J.D. Salinger; "Breakfast of Champions" or "Slaughterhouse Five" by Kurt Vonnegut (plus his collection of short stories in "Welcome to the Monkey House" are really good); and "Gulliver's Travels" by Jonathan Swift (which was written as a satire and not as a children's book).
Just for fun (sci fi): "His Dark Materials" by Philip Pullman; "The War of the Worlds" by H.G. Wells; "Bitter Seeds" by Ian Tregillis (2010); "The Traveler" by John Twelve Hawks; and, "The Space Trilogy" by C.S. Lewis.
You should read "Do Androids Dream of Electric Sheep", The book that inspired the movie Blade Runner. Its actually much better than the movie and damn trippy to boot. If youre into the whole noir detective sci-fi gig.
Hitchhiker's Guide To The Galaxy has a huge impact on me but its not for everyone, its silly sarcastic humor. you should definitely check all Dan Brown books also The Zahir and The Alchemist by Paulo Coelho I want to try the Tomorrow series by Australian writer John Marsden next