What is the theme in The Neverending Story by Michael Ende?

The Neverending Story is Bastian Balthazar Bux' coming of age tale. At the beginning of the novel, Bastian is a friendless, loveless little boy who dislikes himself and others. He withdraws into the fantastical world of Fantastica, which exists only in a storybook. In this fictional land, Bastian can safely explore and actually live out his fantasies. Through a succession of wishes, he first becomes handsome, then strong, then admired by the masses. Bastian begins to forget that he was ever a weak little boy. In forgetting, he suffers from arrogance and begins to believe he deserves all the power and glory in the world. Even his desire to perform good deeds in Fantastica is self-indulgent, as it stems ultimately from his desire to be admired as a great benefactor. The more Bastian transforms himself, the more he forgets his roots. As a result, he is in danger of losing his true self completely.