Martha Grimes' mysteries, all of them, stand in an ordered rank on my bedroom shelves. She's a writer whose stories are worth reading and then re-reading. The puzzle is nearly always interesting and satisfactorily worked out. But that's not the real delight of the novels, only the entertaining excuse for two other more compelling reasons to read her. First, there's her Pickwickian cast of characters. They're a collection of perpetually and ruefully unattached men and women of indeterminate early middle age, who meet in a variety of colorfully named pubs and solve murders with more or less tragicomic flair, while they repeatedly fail to resolve the mysteries of their own inner lives. Second, there's the speculative and philosophical line of thought that often crops up as a secondary theme. Grimes gives this metaphysical aspect full play as a depth and dimension of counterpoint to her vivid characters and solid plot lines. The Horse You Came In On plots an intriguing mystery, but it is about writing, and specifically about plot invention in writing. Let me count the ways--a purported diary from Italy; a minimalist novel; the plagiarized version of the minimalist novel; a holograph manuscript that may or may not have been penned by Edgar Allen Poe; a Russian romance tale made up on the spot to amuse a child; a fabricated family history; a book of poetry; a work in progress (whose writer, to maintain focus, chains herself to her Johns Hopkins University desk--and thereby hangs the crisis of the plot); a hobbyist's attempt at a Dashiell Hammett-style mystery. All these literary productions are embedded in Grimes' own marvelous inventions, carrying us from the Tate Gallery in London to Baltimore, to Philadelphia, to the village of Long Piddleton in Northhamptonshire--just to name the more important locations. It's not often that one encounters a writer who can present thoroughly serious thinking in the form of comedy and at the same time stay competently in the mystery genre. Her novels are pleasing at every level. Her first mystery in this series is called The Man with a Load of Mischief. Start there and enjoy the wandering, speculative, humane, whimsical series of stories. You won't be disappointed.