A teacher addresses her class for the last time, verbally meandering through a variety of topics before hitting the one that keeps all the students transfixed: the teacher's daughter died earlier in the school year due to an accidental drowning, but it was no accident. Slowly the teacher lays out all the information she has, accusing the two students involved, before finally detailing her revenge. Subsequent chapters are written from other characters, each giving their own perspective on the incidents--one boy's mother writes in a diary; one of the accused writes a blog entry. 
 The whole thing is darkly fascinating and disturbingly convincing. Admittedly there are at least three mentally unbalanced characters with sociopathic impulses, but it's hard to say for sure that it couldn't happen, as two of them are triggered by this particular event. 
 I think this was an Alex award winner (adult books with high teen appeal); I think it's deserving of a place in high-school libraries.