“Then he was alone.” With this abrupt opening sentence, Hobbie (Hansel & Gretel) launches readers and her hero—a solitary, homeless kitten whose family has vanished—on an extraordinary trajectory.

“Friends Wanted” reads the sign that Elmore, a self-sufficient but solitary porcupine, posts in the woods. There are no takers—everyone is scared of his quills. “I’m your friend,” says his elderly ...