Science fiction? Detective novel? Metaphysical musings? David Brin's Kiln People covers a lot of bases, but does them all well. It certainly is a detective novel, but this private eye, Albert Morris, lives in a world where anyone can take mannequins made of a certain type of clay and with the right machinery, animate them to act as living beings with some or all of the psyche of the human who animated them. This is an obvious convenience for a detective, as he can make a gray "ditto" to go meet with clients, a green one to take care of the housekeeping, and an ebony one with a special talent for online research, while his organic body catches up on sleep. But the availability of dittos has shaped society in many other ways, from entertainment (thrill seekers can do all kinds of things via a ditto and then "inload" its memories back into their own minds) to transportation (dittos don't have to be made in human shape; life-size dinosaur bodies are imprinted with human minds and used as buses and trucks). But dittos run out of energy and die in about a day, and a ditto can only be animated if a person is physically present to impress a mind onto it -- ditto-to-ditto copies generally don't work out well.
In this fascinating settting, Albert Morris and several of his dittos (all of whom narrate at one point or another) deal with the ongoing hunt for Beta, a criminal who makes illegal dittos of people (the results of making a ditto from a ditto are good enough to be animated sex-toys and such), and also a new case of a missing researcher for the main manufacturer of ditto bodies. Multiple narrators in a story often become a bit confusing for the reader (from Robert Heinlein's The Number of the Beast to Toni Morrison's Beloved) but in this novel the technique yields complete clarity, whether it's because each chapter starts with a sentence or two stating who is speaking, or because in a way, it's always Albert talking, even when there are three or four Alberts who have lived completely different experiences during the last day.
Particularly interesting is the green ditto who "goes Frankenstein" -- abandons the chores he was created to do and goes off on his own. His story brings up the question of whether he is less or more like the original Albert than those dittos who quietly go about their assigned tasks. Other people's dittos also go Frankenstein, and the reader sees the many ways a psyche can seem to act against itself, but in their case it's only from an outside view. "Frankie" carries the burden of showing these variations to the reader from inside and he accomplishes that while leading into the climax of the book, which is both a solution to both mysteries and a further example of what the latest ditto research might say about the human mind and soul. The setting is fiction, but while reading you never think that the persons aren't completely real.