Sturgeon is excellent at conveying the emotions of children--a talent on ample display in this 1950 novel. Crystalline, jewel-like aliens, intelligent but utterly incomprehensible, exist on Earth; as part of their life-processes, they sometimes produce flawed copies of objects, animals, or people. But the rare paired jewels produce perfect copies--like young Horty, an apparently human lad who runs away from home and joins a carnival, where he's befriended by midget Zena and the other carnies. The carnival's owner, however, is a vicious, amoral doctor, the ""Maneater,"" who knows about the jewels: he can cause them great pain and thus force them to do his bidding. (He controls Zena by controlling the crystal that made her.) So Zena, who recognizes that Horty is a jewel-being, helps him to develop a secure human personality. . . in preparation for the ultimate showdown with the megalomaniac Maneater. Overall: flawed but thoughtful, often fascinating--with a potent theme (how to define humanity?), the brilliantly conceived alien jewels, and the usual Sturgeon weaknesses (disjointed plotting, pulp-ish patches) in the narration.