The 100 by Kass Morgan

Colonists have been living on a spaceship for years, and now they are considering returning to Earth. The chancellor sends one hundred convicted teens to the planet rather than sentencing them to death. The colonists will know it's safe to return if these teens are not killed by the radiation levels. Wells, the chancellor's son, gets himself convicted of a crime in order to travel to Earth with Clarke, a girl he loves. She doesn't return his feelings, since Wells was responsible for the execution of her parents. Meanwhile, Bellamy uses force to get on the shuttle, so he can protect his sister. During the commotion, Glass escapes the shuttle and sneaks back onto the spaceship. The teen convicts must survive the strange, new planet, and the spaceship colonists must face their own unexpected crisis.

The plot follows the stories of the main characters; different chapters focusing on each one. Clarke struggles with her mixed feelings for Wells, and she's the only convict with medical knowledge. Bellamy struggles with being accepted by the others, and his sister has a secret conflict. The book deals with overpopulation, since unauthorized babies on the spaceship are killed by the government. The ship also has different social levels that creates a conflict. Glass is from the highest class, but she's in love with a boy from a lower class. The book will give you a lot to think about. There is a sequel to it.