Coming of Age; Young-Adult Literature
Getting kidnapped isn't the way teenagers normally transition from the innocence of childhood to adulthood, but nonetheless, Gemma's experiences still qualify as a coming-of-age story.
When we first meet her at the airport, Gemma's life is relatively limited—beyond her best friend, Anna, her crush on Ben, the annoyance of Josh, and her relative contempt for her parents' superficial, meaningless professions, there's not a lot of serious stuff going down. Really, she's just an average girl.
Then, Ty swoops in and changes all of that. All of a sudden, this suburban London 16-year-old girl finds herself cut off from civilization in the middle of nowhere, with her kidnapper as her only source of companionship. Talk about girl meets world—the trials and tribulations of social politics and parental struggles just got pretty small.
As a result, Gemma has to learn to think on her feet in order to survive, learning to find outlets for escape, psychologically outwit Ty, and attempt to keep herself safe from whatever dangers he and the desert might pose. "I don't know how I was remembering to do it all," she says of driving the car when she attempts to escape from Ty. "It was like a different part of me had taken over, a more grown-up, logical part that remembered these things" (54.10).
As for young-adult lit, since this is a teenager's story through and through and it is written in a creative and engaging way, it's definitely targeting Gemma's peers as readers.