"...He knew it. She didn't. She couldn't understand why she did what she did. She was always sorry later, but she couldn't stop while she was doing it, and acting out."
This is Jesse, and her way of dealing with life. She always been the "other sister" the bad sister, the sister who always feels inferior to her older sister Lindsey. She is completely misunderstood until someone looks deep enough to see the real her.
I am a sucker for these tortured souls, I always seem to feel for them, and when a book compels me to feel this deeply, I think it means I liked it. So, yeah I liked it.