This is an incredibly well told story that kept me guessing right up until the very end. Admittedly, I did not like the ending, but others have said they did enjoy that particular twist, so this is more my own personal tastes coming into play than anything inherently "wrong" with the story. (This is also the sole reason I did not give the book a full five stars; I wish I could give it 4.5!)
The book is steeped in Japanese folklore and mythology, and uses quite a few terms that English readers might not be familiar with, but the author weaves them in without fuss and provides enough context to discern their meaning without distracting from the story. I rather enjoyed learning something new!
In sum, highly recommended, but keep on your toes as you read! :)