The book is better than the movie and contains a number of wonderful vignettes that are not in the film. For example, as the boys built more complex rockets, Homer realized that they needed to learn calculus to take the next steps in rocket design. Homer and the science teacher convinced the principal of the high school to offer a new course in calculus. The enrollment was limited to six people, the exact number of boys involved in the effort to make the rockets. No one expected anyone else at the school to sign up for the class. However, the girl that Homer had a crush on signed up too, and since Homer's grades in math were the worst of any of the applicants, he was excluded from the class. The principal at this point was not sure that the Rocket Boys were really up to any good and called them "bombers," a reference to their first effort which had blown up Homer's mother's fence. The principal would not increase the enrollment in the class by one person to allow Homer to take it. Initially, Homer felt that his dreams of a career in rocketry were over, but in the depths of his depression, he found a calculus text on the bookshelf at home. There were notes in the book in his father's handwriting showing that his father, who had never gone to college but who was called upon to supervise engineers, had taught himself calculus. Homer began to study the text and the other members of the club helped him. Homer learned calculus without the class, to his own amazement and that of his teachers and the principal.