Real-Time Rendering by Eric Haines, Tomas Akenine-Moller, Tomas Moller (2002, Hardcover, Illustrated)

At $23, this book was a steal. The 3rd Edition was just released, and is worth every penny, but it costs a lot more pennies than this edition. If you are picking this book up for class, or don't need thorough coverage of cutting-edge techniques, the 2nd edition will more than likely have everything you need. Very interesting and readable.