God's Debris is an excellent book to make you think. It's a thought experiment that is supposed to make you look at the world in a completely new way and twist your brain.
Next, anything by Michael Crichton. Jurassic Park, Lost World, Andromeda Strain, Rising Sun, Sphere, Disclosure, Airframe, Eaters of the Dead, The Terminal Man, they are ALL EXCEPTIONAL! I strongly recomend Michael Crichton. Not a single book I would rate below 9.5 out of 10. Jurassic Park would be a great start. It's 10x better than the movie.