Here are a few good ones, off the top of my head, and in no particular order:
Path of the Paddle, by Bill Mason (the bible)
Dangerous River, by R.M. Patterson (puts everything in perspective)
Unflinching, by Edgar Christian (rare book, when things go horribly wrong)
Canoeing Wild Rivers, by Cliff Jacobson (bible # 2)
The Starship and the Canoe, by Kenneth Brower (just a great story, and all true)