Mystery fiction is a genre of fiction typically focused on the investigation of a crime. Mystery fiction is often used as a synonym for detective fiction or crime fiction—in other words a novel or short story in which a detective (either professional or amateur) investigates and solves a crime mystery. Sometimes mystery books are nonfictional. “Mystery fiction” can be detective stories in which the emphasis is on the puzzle or suspense element and its logical solution such as a whodunit. Mystery fiction can be contrasted with hardboiled detective stories, which focus on action and gritty realism.
Guardian Unlimited Article from 2000 celebrating Agatha Christie’s long-running mystery play The Mousetrap on London’s West End.