Valencia asks if Billy wants her to bring him any books.
Billy says he's got plenty—he has access to Rosewater's science fiction collection.
Billy asks Rosewater (who's sitting in the next bed) what he's reading.
It's another Kilgore Trout novel: The Gospel of Outer Space.
The hero of the novel is an alien (who looks like a Tralfamadorian) who wants to know how Christians can be so cruel.
He decides that the problem is the New Testament. It's supposed to teach people to be merciful, but what it actually seems to teach is this: "Before you kill somebody, make absolutely sure he isn't well-connected" (5.30.7).