This is what a psychological thriller should be. It's gruesome but not grossly so. There's a lovely build to the tension and that final release of action at the end. 

Kirino's dissection of human behaviour is masterful. Just like how her characters chopped up dead bodies. Each character is wonderfully detailed and vivid. 

My only bug bear was the resolution scene at the end. When the two main characters face off then suddenly one becomes sympathetic to the other. It's like crunching on something unexpected and slightly unpleasant at the end of a delicious meal.