"Zinn & the Art of Road Bike Maintenance" By Leonard Zinn (also has a mountain bike version which I expect to be equally good, but I've not read that). The illustrations are generally basic but to the point, and he covers a lot of ground -- all styles of bottom brackets, shift levers, etc, and outlines most of the tools you need. You'll have no problems figuring out how to disassemble/reassemble your bike (and you'll probably decide to rebuild a number of components along the way).

Also, don't forget great online resources like the park tool website (http://www.parktool.com/blog/repair-help).

*Edit: always fun to discover you're replied simultaneously as someone else with almost the same information!