“Gritty” procedurals and more “psychological” detective stories (often involving serial killers whose identities you know from page 1) are also often just grown-up puzzles, not real mysteries. Mysteries in the sense of weirding truly begin in the post-Christie era, though Christie herself saw it coming, in her pushing-the-envelope plots (The Murder of Roger Ackroyd, Murder on the Orient Express, and most significantly, Curtain, Poirot’s last case, which is almost a true mystery).
