"The 100" is a young adult science fiction book series written by Kass Morgan. It is set in a post-apocalyptic world where Earth has been devastated by nuclear war. The story follows a group of 100 juvenile delinquents sent back to Earth from a space station called The Ark to determine if the planet is habitable again. As the characters navigate their new environment, they face challenges such as survival, conflict with existing inhabitants, and the complexities of their relationships. The series explores themes of leadership, morality, and the consequences of human actions, making it a compelling read for fans of dystopian fiction.