The Secret Place by Tana French

St. Kilda’s, an all-girls boarding school in Dublin, is an ecosystem unto itself. The outside world almost never intrudes. All until Chris Harper, a student at a neighboring boys’ institution, is found murdered on Kilda’s grounds. Convinced she knows who did it, one of the girls leaves a note on the school’s anonymous board. I KNOW WHO KILLED HIM, the note says. Tana French’s brilliant and cerebral mystery is also a stellar exploration of complicated teen dynamics and friendships; the years when the focus is relentlessly on the now and tomorrow is forever held at bay no matter the costs.