A Scanner Darkly by phillip k. dick is a good one
But if you really want to have to think, read the classics. Brave New World, Lord of the Flies, Anthem, Cry the Beloved Country, Adventures of Huckleberry Finn, Animal Farm, 1984, Catch 22, Slaughterhouse Five, One Flew Over the Cuckoo's Nest, Cats Cradle, Breakfast of Champions......The list goes on and on but these are some of the ones Ive read. Not only are these books terribly enjoyable, but they offer an expanded view on the world, social behavior, human nature, and power, and they will surely help you to become a more open minded, and analytical person. They make you ask questions about yourself and the world you live in and for that they are the best books and why they are considederd classic.