A Short History of Nearly Everything by Bill Bryson (Non-Fiction).
It's a laymans guide to the history of science and an enjoyable read. There are bits that apparently get lost in translation when Bryson tries to decipher some of the more theoretical topics, but this isn't meant to replace textbooks or research articles. If you like the Discovery channel but sometimes find yourself wanting a little more, you'll probably enjoy this book. I have particularly enjoyed some of the analogies he makes (quotes?): if you reduced the Sun down to the size of a pinhead, Pluto would still be 35 feet away, and the outer edge of our solar system (everything within the gravitational field of our sun) would still be farther away than the eye could see (the edge of our solar system is tens of thousands times farther away than the distance to Pluto). Those sorts of quotes really altered my perception which was mostly based on those illustrations in my old science textbooks (you know the ones which show all the planets in relation to the Sun, complete with Mars being in the shadow of Jupiter, etc.) There are many great analogies like that which really help to gain a perspective on how complex and amazing the natural world is, and how insigificant and temporary modern man is in the age of earth and the universe.