The Kohga Ritual (War of the Ninja Master)

Remember all those cloned men's adventures books that filled the men's adventure sections in bookstores back in the 70s and 80s? This is not one of them. I have read the series enough times that I am begging for it to released in eBook format. I hate spoilers and will not throw them out here. Let me just say that the whole world is connected and, in this series, Brett Wallace travels to corners that are not only dark, but profound.