If you're looking for a thriller type book and haven't read it yet, I recommend Misery by Stephen King. I'm assuming you're 14 - 15. I read it when I was 14, around your age (wow, that makes me sound old; I'm 2 months into being 16), and it had my heart pounding from the very start. It has a strong beginning and a strong ending, and isn't super long like many other King novels.
The basic gist of it is: narrator is a bestselling author. Narrator stupidly drunk drives in a storm after finishing a novel. Narrator shatters his legs and pelvis, wakes up in a woman's home. Woman turns out to be nutty, and also his BIGGEST FAN! She keeps him captive and 'treats' him. What could possibly be off about this situation? And what harm could our precious narrator come to in the hands of a not-very-qualified nurse, miles away from civilization, with no real ability to defend himself?
Lots of viscerally terrifying scenarios and blood and misery (cymbal crashes play in background) await our poor hero! Perfect!!!