The Three Coffins Author:John Dickson Carr The police called him the "invisible murderer..." He killed his first victim and literally disappeared. He killed his second victim in the middle of an empty street, but with watchers at either end -- yet not a soul saw him commit the crime and no footprint appeared in the snow. — It was terrifying, baffling, impossible. But the corpses proved it... more » was happening.
A wonderful book from a writer whose mysteries range from top notch (this one) to basically unreadable.
This is generally considered the zenith of locked room mysteries, and contains the famous "locked room lecture" in which Gideon Fell enumerates the various ways in which a murderer can do his deed and make it seem impossible.
In a poll conducted for his anthology "All But Impossible," Edward D. Hoch asked a number of mystery writers to name the best miracle-crime novels, and "The Three Coffins" topped the list (Second was Hake Talbot's "Rim of the Pit."