new movie that came out. book written in 2003.

Ember is a self-contained city, constructed over 200 years ago by "the Builders." It is the only known settlement of humankind in a world of total darkness.
All food and supplies come from giant storerooms under the city and a handful of greenhouses. All the light in the city comes from the lights placed all around the city. The electricity in the city comes from an ancient hydro-electric generator in the underground Pipeworks. Beyond the borders of Ember are the dark Unknown Regions, which are impossible to explore.
The story begins after the construction of the city. Two of the Builders discuss what will happen when supplies run low and conditions become bad. They leave instructions for the citizens in a special sealed box which will open automatically after 200 years when it should be safe to leave the city.