There are no 'classics' of crime and detection. Not one. Within its frame of reference, which is the only way it should be judged, a classic is a piece of writing which exhausts the possibilities of its form and can never be surpassed. No story or novel of mystery has done that yet. Few have come close. Which is one of the principal reasons why otherwise reasonable people continue to assault the citadel.

Introduction - The Simple Art of Murder (1950)