The Elegent Universe by Brian Greene. Great book on the basics of relativity, quantum mechanics and string theory using little to no math, so it's really accessable.
Yep, that's a good one.
Another one I like, The Whole Shebang
by Timothy Ferris, is a little older, so not completely up to date anymore. What I really like is that Ferris explains cosmology and the theories and mechanics behind it in such a way that doesn't require the reader to possess a heavy background in the field, and it's much more readable (and somewhat closer to current) than Hawking's Brief History
, which can get a bit thick in places.