Stanley's thrilled for bookmobile day--until the old man at the window refuses to lend him the story he wants, all because it features a girl. "Girl books" are only for girls, the book man insists, just like cat books are only for cats and robot books are only for robots. But when a dinosaur arrives at the bookmobile and successfully demands a book about ponies, Stanley musters the courage to ask for the tale he really wants--about a girl adventurer fighting pirates on the open seas. By speaking up, Stanley inspires the people, cats, robots, and goats around him to read more stories outside their experiences and enjoy the pleasure of a good book of their choosing.

When the bookmobile librarian refuses to lend Stanley the story he wants, he learns the importance of advocating for the book of his choosing, and in doing so teaches the librarian the virtue in allowing everyone to select the stories they enjoy.