Crank by Ellen Hopkins
This is an important part because, while visiting her father, Christina meets Adam/Buddy for the first time and she meets the monster, crank, for the first time. She falls in love with Adam while under the influence of the monster.
Christina leaves her father, and returns to Reno and her mother’s house. This is an important part because Christina finds the monster again when she meets Chase and Brenden. Both of the boys do monster with her. Brenden wants to have sex with Christina, and only stops from forcibly having his way with her because she says she is a virgin. Chase seems to really care about Christina, but he isn’t happy when he finds out that she is with Brenden.
After riding with the monster for a few days and then trying to go to the first day of school, Christina realizes that she has started down a bad path. She vows to be a good member of her family, go to school, do her schoolwork, and stay away from the monster. Things go good for a while, and she is getting into the rhythm of school, but the monster is always on her mind.
I predict that Christina will not keep her vow. I think she will go back to the monster, and lose her virginity to Brenden. The monster will make Christina abandon her schoolwork and her family.