This book, obtained from the Portsmouth Public Library, was on Tom Nolan's WSJ list of the Best Mystery Books of 2019. Three down, seven to go. The author, Anthony Horowitz, is a British writer mainly known for his television work (Foyle's War, some early episodes of Midsomer Murders, etc.) and juvenile fiction.
And the narrator in this book is named Anthony Horowitz, a writer working on Foyle's War, author of juvenile fiction… Oooh, that's kind of a neat trick! So it's not clear where the dividing line is between fiction and reality here. This book is the second entry in a series, but there's not a lot of reference to the previous book.
Anthony's writing talents are enlisted by ex-cop Daniel Hawthorne who has (in turn) been asked by the actual cops to help out on a murder investigation. Anthony is, to a first approximation, the Watson to Hawthorne's Sherlock. It is a mystery in the classic form: a lot of clues, a lot of possible suspects, a complex history that needs unravelling.
The (initial) victim is a divorce lawyer, bludgeoned with a bottle of expensive wine, then stabbed to death with the shattered bottle. Gory! But who's to blame? The lady poet screwed over (or was she?) in the lawyer's latest case? Or her ex-husband? Or does it have something to do with the lawyer's participation in a long-ago caving expedition which resulted in the accidental death of one of the spelunkers?
Complication: the unpleasant lady cop also assigned to the case despises Hawthorne, and attempts to blackmail Horowitz into disclosing what Hawthorne's uncovered, so that she can beat him to the solution.
There's also a complex relationship between Horowitz and Hawthorne; Hawthorne's not a particularly pleasant person, with a mysterious past of his own. Horowitz tries (not particularly successfully) to unwind some of that.
Bottom line: a good read. Now on to the next book in Nolan's list…