See also 宮部 みゆき (Japanese language profile) and 宮部美幸 (Chinese language profile).
Miyuki Miyabe (宮部みゆき Miyabe Miyuki) is a popular contemporary Japanese author active in a number of genres including science fiction, mystery fiction, historical fiction, social commentary, and juvenile fiction. Miyabe started writing novels at the age of 23. She has been a prolific writer, publishing dozens of novels and winning many major literary prizes, including the Yamamoto Shūgorō Prize in 1993 for Kasha and the Naoki Prize in 1998 for Riyū [The Reason] (理由). A Japanese film adaptation of Riyû, directed by Nobuhiko Obayashi, was released in 2004.
I feel quite ambivalent about this book. On the one hand, it is fun, it is a page-turner, the story is simple but compelling, and Miyabe's knack to create interesting youngsters is as good as ever. On the other hand, it feels more of the same, and, really, nothing actually happens. You could jump from the ending of book two of the series to the fourth and probably be able to follow the story without many problems.
Because... Well, what does really happen here? Ryōko decides that, as Kashiwagi's death is still a mystery, the middle school students that were of the same year as the deceased have to organize a 'mock' trial and find the truth behind the death... Cue pages and more pages of easy to read conversations, with interesting (but a little bit stereotypical, particularly the adults) characters, and some head-scratching situations that border on the unbelievable. And little, or none, plot development.
Fun, but one has to wonder what was Miyabe thinking when she decided to stretch the story so thin.
The best: a page-turner
The worst: it is just air, page after page of nothingness
Alternatives: well, read the first two or Miyabe's own "Brave Story"... but, today, and just for today, I will recommend manga instead of other books. Manga with middle or high school students at their center: "Slam Jump", "アゲイン!!" ("Again!!"), "響" (Hibiki), "センセイ君主" ("My Teacher, My Love")...