The Judas Window (John Dickson Carr)

Carr specialized in just one type of mystery: the so-called "impossible crime." A person is murdered while alone in a locked room, or under view of witnesses, or in the middle of a snow-covered field. If you like detective stories with excellent fair-play puzzles and lively, if sometimes shallow, characterization, you should check him out. The Judas Window is a great place to start!