This writer not only doesn't apply the show-don't-tell principle, he rather opts for the tell-five-times-or-maybe-a-sixth principle. Boring descriptions, underdeveloped & flat characters, monotonous style. The core story mechanic could have some potential if the final twist hadn't thoroughly ruined it. In short, though not actively terrible, not worth the time required to read it (or the paper it's printed on, for that matter).
An entertaining mystery story based in a Japanese school. Was not a terribly challenging read. I did find it a bit repetitive at times and at least part of the end seemed fairly predictable. Nonetheless mostly enjoyable read and a good mid N3 N2 level book.