Hi Justin, I asked the same question a couple of months ago. Our booksexpert Jo didn't even know the book (to his own surprise :-)) I didnt read very good reviews on it so I still haven't bought it. But its very tempting..... I believe Jan knows it..
The guy has a Facebook site that he posts Samurai facts on each day. He was pumping the book yesterday on a post about Teppo, and how had the weather the night before the battle of Seki ga Hara not been so wet and made the powder and fuse supply unusable, the death toll would have been greater. Then said read his book....
"The book is alright. There is some minor errors in the text and the pictures are somewhat nasty, due to cutting production cost I imagine. But I found it quite enjoyable. The outlet of new books dealing with Japanese history are few and far between, so I guess beggers can't be choosers..."
But the books is pretty expensive, thats for sure.
The author is right about the weather influencing the performance of the teppo on the day of the battle. Damp gunpowder probably saved the life of many men. But it was truly a bloody battle, damp powder or not.