Books at the Wal-Mart

Visiting the local Wal-Mart this evening, I noticed in the book section a book titled something like The Boy Who Visited Heaven and Came Back. Right next to it were rows of vampire novels of different sorts. The cover of the boy-book did not say whether he had an insatiable thirst for the blood of living. Still, my local readers have a great fascination with people coming back from the dead. What I don't understand is whether they can tell that both sorts of books are fantasies or whether they believe one set of them is real and the other fantasy. If so, I don't know how they tell the difference.