Yup, it is a good mind-fuck book with a brilliant, unexpected ending. Some reviewers/readers have already pointed out it is nearly impossible for non-Japanese readers to figure the mysteries out on their own because the mysteries are heavily linked with the author's word-play with certain Japanese words, but guess what, I am okay with it. I'd made a few guessing of my own but none of them had ever come close to hitting the marks, but it is a defeat which I have no problem to accept.
Will keep my eyes on more of this author's novels.