The Word Is Murder by Anthony Horowitz

Diana Cowper, attends a funeral parlour to arrange her own funeral and a few hours later, she's found murdered in her home. Disgraced detective Daniel Hawthorne, a brilliant but eccentric investigator needs a writer to document his investigations, and convinces the real Anthony Horowitz (acting as a fictionalized version of himself) to take the job. As Anthony gets pulled into Hawthorne's world, they delve into Diana's past, uncovering a hit-and-run accident from ten years ago. Secrets and lies from various suspects cloud the investigation.  A weird piece of metafiction where Horowitz inserts himself (and a lot of his career details) and Hawthorne into a "Sherlock and Watson" type whodunnit.  As always, the novel is very well written and the breadcrumbs to the dénouement well hidden.  A most intrecate and engaging novel. 5/5