Great story, engaging and interesting mystery.  Like all great mysteries, this is Yokomizo's locked room mystery.  I enjoyed the setup, the description, and the characters.  I also enjoyed the pace of the book, fast enough that you moved through the story at a good pace, but slow enough to enjoy some back story and local history and a peek into a rural family in pre-globalized Japan.

It also name-dropped some classic western and Japanese mysteries I would be interested in picking up (it doesn't spoil them).  My only complaint is that it was difficult to follow the characters (a character tree may be a must for a western reader) and it didn't also include the names of town, places and people just H--- and D---, which is common in some translated works but it is annoying.