Yagyu Munenori The Life Giving Sword
I read this book last fall and was really impressed; especially by it's great capacity to complement the study of Kendo. I was surprised that I had not heard of the book before, so I did a little googleing -- with the expectation of finding all kinds of hails and praise for Yagyu. Instead, I found a whole bunch of wishy washy comments on various Eastern Philosophy blogs. From what I gather, the book's first English translation was in 2003, so not so many Westerners have read it. Maybe it will pick up a better following in years to come....or maybe you just have to be a kendo-kai.