"The City of Ember" is a novel by Jeanne DuPrau that tells the story of a city built underground to protect its inhabitants from a disaster on the surface. The city relies on a failing generator for electricity and has limited resources, leading to a sense of urgency among its citizens as they face the threat of darkness. The main characters, Lina Mayfleet and Doon Harrow, are determined to find a way to save their city. As they explore the mysteries of Ember, they discover clues that may lead them to a way out, highlighting themes of hope, perseverance, and the importance of community.