If you went to school to learn how to write locked room mysteries, this book would earn you a PhD, not to mention a publishing contract. Carr knew every possible trick in the genre, and his novel is filled to the brim with them. There’s also a lecture on the nature of locked room stories and ‘perfect crimes’ inserted into the narrative (in chapter 17) that can stand alone as a work of literary criticism. They should assign it in college lit crit classes, and perhaps at the police academy too.