I'm currently reading Matt Hill's Graft, which is so named because it features a woman named Y with three arms. One growing out of her back, and it's artificial. And appropriately enough for the name, I don't really know why she does. Admittedly I'm only about halfway through, so when I'm finished maybe I'll get it. Her voice and memories have been taken away, which makes it look like some kind of slavery, although there are also indications she signed up for this treatment. But I don't entirely see why this kind of body modification is worth the trouble.
Hill writes fairly well, which is one reason I haven't given up on the book. But his best writing tends to focus on relatively ordinary carjackers, madams, and hit men. He might be better at writing straight noir crime fiction set in the North. Maybe the biological engineering is so his book can be sold in the sci-fi section?