+1 to The Simon Singh Book. Very good indeed. My recommendations (some science/maths stuff, some political/religion):
Longitude - Dava Sobel
Infidel - Ayaan Hirsi Ali
The God Delusion - Richard Dawkins
Nickel and Dimed: Undercover in Low-wage America - Barbara Ehrenreich
Godel, Escher, Bach: An Eternal Golden Braid - Douglas R. Hofstadter