The City of Ember

A and I also read The City of Ember so that she could go see the movie with Brad. The story is set at some future date after some disaster that threatened to wipe out humanity. The “builders” created an underground city to preserve a remnant of humanity for 200 years. They left behind instructions on how to exit the city, but they have been lost and it’s now 200-some years later and all the supplies are running out and the generator that powers the city is nearly permanently broken.
Two young adults (age 12), Lina and Doon, have just graduated from school and been assigned their jobs in the city. Lina lives with her 2 year old sister and her grandmother, her parents having died of a disease that killed many in the city around the time her sister was born. Lina’s sister finds the box with the instructions for the exit in the closet and starts to eat the instructions. Lina rescues them, but can’t figure out what they mean with large chunks missing. Meanwhile, Doon is exploring the pipeworks below the city. When Lina shows Doon the paper, he’s able to piece together what they mean based on his explorations.
Lina and Doon tell the mayor of their discoveries and are branded criminals, but a fortuitous blackout allows them to escape out the exit and after a harrowing journey, reach the outside world where there is nothing but wilderness. They are able to find a hole to above the city in a cave nearby and drop a note down with directions for everyone to get out.
This book is also highly recommended.