In case you haven't experienced Richard P. Feynman, try these books out:

Six Easy Pieces: A book made for people with no experience with math or science. Even then, it manages to describe atoms, thermodynamics, relativity, quantam mechanics, etc... Just the fact that Feynman managed to explain all this to the everyday person is proof of his genius.

Six Not-So-Easy Pieces: The next step up from Easy Pieces. It deals mainly with Relativity, and has a bit more math involved than easy Pieces did.

The Feynman Lectures on Physics: This is a three volume set of what was supposed to be the freshman and sophmore physics textbook at Cal-Tech. It covers vectors, E&M, relativity, quantum mechanics, most everything except string theory. The 12 pieces in Easy Pieces and Not-So-Easy Pieces are actually 12 lectures out of these three volumes.

Surely You're Joking, Mr. Feynman!:Taken from apirkle above... A collection of anecdotes about his life. A truly excellent book...you should go read it now.

What Do You Care What Other People Think?:Taken from Xydexx Squeakypony... a collection of Feynman stories, though I don't think it was written by Feynman himself. It's a followup to "Surely You're Joking..." Note: I haven't read this one myself, I will as soon as I get the chance.

Feynman Lectures on Computation:Taken from chinoodle... You should also add "Feynman Lectures on Computation" which I cannot recommend enough to all Computer Science undergraduates .. it should be required reading

The following I have been notified have also been written by Feynman, though I have not read them myself. Thanks st.augustine for pointing them out!:
The Meaning of it All
QED
The Pleasure of Finding Things Out

If I missed any (I'm sure I have, these are only the ones I have read) please /msg me and tell me what to add on this list!