I finished reading The Technique of the Mystery Story by Carolyn Wells, 1913.
Yes, that’s 1913.
Wells wrote this when the mystery story was still comparatively young, but surprisingly, not much has changed in the last hundred years, from the chapter on getting mysteries accepted as literature, to the missteps and clichés of the time, which are still missteps and clichés. Her advice on writing mysteries is still good, if in some places more amusing than intended because of the intervening years (Don’t have the butler be the murderer – it’s been done to death).
What I found most useful to me was the history lesson, that is, her interrogation of the mystery writers and their protagonists who were popular at the time (and still important to read if you are a fan or a scholar of the genre), and a historical analysis of the changes in the genre from Poe to 1913.
This is a quality read. It’s available on audio from Librivox for free since it’s out of copyright, although the reading is done by chapter and by several people.) or you can probably find a copy on ABE books or the like – maybe even in the library.