What is the theme in About a Boy by Nick Hornby?

Another important theme is coming of age. Marcus is twelve, which is an age at which a boy is slowly beginning to make the transition from child to adult. Marcus is struggling, however, because he has been forced to grow up quicker than most boys of his age. Marcus has to deal with his mother's depression as well as his own social problems at school. Marcus begins to think that he needs to expand his family, to have a father he can turn to in times of crisis, a cushion to keep him from being alone so much.