[I've been
The Book of Five Rings

I think I was looking for something a little more metaphorical but this book which outlines the principles of being a good swordfighter--written by Musashi in the 1650s--has a lot of good stuff to know in addition to, you know, learning to kill people with your sword. It’s also a lovely book and this re-issuing of it by Shambhala with translator notes by Wilson is an all-around interesting experience which is not just about learning swordfighting but also about learning how to take a scroll from the 1650s and turn it into a book in the 21st century.