The City of Ember (book)

The City of Ember is a post-apocalyptic children's novel and the first in the The Books of Ember series. It follows child protagonists Lina Mayfleet and Doon Harrow as they search for a way out of the titular city of Ember, which is beginning to suffer increasingly prolonged and dangerous power failures.

Publisher's Summary
Citizens of Ember shall be assigned work at twelve years of age...

''Lina Mayfleet desperately wants to be a messenger. Instead, she draws the dreaded job of Pipeworks laborer, which means she'll be working in damp tunnels deep underground.''

''Doon Harrow draws messenger — and asks Lina to trade! Doon wants to be underground. That's where the generator is, and Doon has ideas about how to fix it. For as long as anyone can remember, the great lights of Ember have kept the endless darkness at bay. But now the lights are beginning to flicker. . . .''