What is the theme in Stormbreaker by Anthony Horowitz?

Family is a theme in the book. The book begins with Alex learning that his uncle, the only parent he has ever known, has been killed in a car accident. Alex is devastated by this news, but it does not keep him from trying to learn the truth about his uncle's death. Perhaps it is Alex's grief that leads him to seek the truth, but whatever inspires him, Alex is determined to find the man who killed his uncle. This determination, however, does not include joining the MI6 at the age of fourteen.