Ayako is, easily, one of the best graphic novels that I've ever read and certainly the best I've read this year. It's twisted, sick, depraved, violent, and absolutely engaging. It's a very different take on the familial unit, showing a family that while fatally flawed will remind you of your own in a lot of different ways.
The art of the book is beautiful. Its pace is quite brisk and the dialogue, even in translation, is complex and beautiful. The closest thing I can think of to this book is that it is a faster-paced version of a Ingmar Bergmann film. It has the darkness and subtlety of that director's films while still bringing the author's own voice in.
I think that this is a book that many can enjoy, but like in the other reviews, it has a number of problematic components. When understood in the context of the story, most of them can be forgiven as the author intends. The ones that cannot move the story forward. In the end, this narrative requires the intense darkness of the story, otherwise it would not be nearly as engaging.