Cover has come loose from the book proper. Cover shows some creasing, corners bumped, 1/2" tears at top and bottom of spine. Initials on ffep, some foxing, text is quite clear.
Lancer # 73-814 appears to be a 1969 reprint of the 1966 paperback original.
"One mad killer. . . Jack the Ripper, the most depraved murderer the world has ever known. Two great detectives. . . Ellery Queen and Sherlock Holmes, match wits in a unique duel to solve a baffling mystery."
"presented with the full approval of the estate of Sir Arthur Conan Doyle and is a legitimate addition to the Holmes canon."; 16mo - over 5¾" - 6¾" tall