It is called "The secret to teen power", Great book to becoming a positive person!
Buddhism Plain and Simple is another good, concise little introduction.
Once you're accustomed with the basics of buddhism then it's time to get out the big guns and read The Dalai Lama's books, How To Practice and The Art of Happiness.
Also interesting is the story of Tenzin Palmo, a woman who devoted her life to becoming a buddhist nun and spent 12 years happily meditating in a cave.
Hope that's some help!
The books mentioned are all helpful to a point, having a little flick through the Pali Canon is advisable (not as scary as it sounds!) as you will quickly get a feel for the central tenets of 'Buddhism' per se rather than the scholastic biases of Buddhism put forth by people like the Dalai Lama. Something like Gombrich's What the Buddha Thought might help, too.