Original answer published on Quora; this is an expanded answer.
Authors often have ideas for their titles, but the publisher usually has the last say. Publishers are often better at meeting reader expectations when it comes to titles, covers, and book descriptions than the authors themselves.
Sue Grafton came up with the idea for titling her alphabet mysteries (A Is for Alibi, B Is for Burglar, C Is for Corpse). J.K. Rowling came up with Harry Potter and the Philosopher’s Stone, although Scholastic famously changed it to Sorcerer’s Stone because they thought American children would reject anything having to do with philosophers. Stieg Larsson’s original title for The Girl with the Dragon Tattoo was Men Who Hate Women. And Faith Martin’s DI Hillary Greene series, about a British detective who lives on a narrowboat, originally had “Narrow” in all the titles: A Narrow Escape, On the Straight and Narrow, Narrow Is the Way, By a Narrow Majority. When Joffe Books republished them, they were retitled with “Murder” in all the titles, probably to ensure that readers knew they were getting a murder mystery (Murder on the Oxford Canal, Murder of the Bride, and the abysmally titled Murder at Home and Murder at Work). The Joffe titles, though not as clever, seem to be selling very well—much better than the original titles (yes, even Murder at Home and Murder at Work).
I struggled for weeks to get both of my books titled. Much like Faith Martin, I had an idea for the Fenway Stevenson mysteries' titles that focused on an aspect of my main character. Because Fenway was named after a famous baseball stadium, the books' titles would be common baseball-based sayings that would be relevant to the plot. Out of the Park was the original name of The Reluctant Coroner. The title of book two was originally The Perfect Game. And I had a few titles in the running for future books: Runners at the Corners, A Shot Down the Line, and so on. Fortunately, I realized that these titles didn't sound like murder mysteries, they sounded like baseball dramas. And I wasn't writing a sequel to Bull Durham—I was writing detective fiction. I didn't want anyone picking up The Perfect Game and be disappointed that it wasn't about a late-innings pitcher's duel. (In addition, baseball isn't popular in some of the major international book markets, which made the decision to go with mystery-centric titles much easier.)
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