I bought this book on 6/18 at Powell's Books in Beaverton, OR (a branch of main store in Portland) for $2.95

c. 1935 -- 222 pages -- Paperback -- IMBA's 100 Favorite Mysteries of the Century

Back cover: A spine-chilling mystery by the master. 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 was happening!