A BOOK OF FIVE RINGS (http://www.miyamotomusashi.com/gorin.htm)
"Go Rin No Sho"
by Miyamoto Musashi
Great book! I read it in my youth (and several times since) and find that it applies to many situations. Who says self-help is new :).
Here's another good translation - http://www.samurai.com/5rings/ (http://www.samurai.com/5rings/).