The concept of a Japan-like culture was an interesting idea to work from, but the whole book was rather tame.
I persevered for the first couple of hundred pages, without exactly being gripped by any of the events. The descriptions seemed to be sparse, as if the author was too embarrased to describe some of the scenes, and not comfortable with any of the battle scenes. The last few chapters were slightly more interesting, perhaps because I was glad that I had nearly reached the end.
All in all it seemed like a children's author trying to get a bit more risque, but failing.