Hundreds of years ago, a disaster struck earth. It was no longer possible for the human race to survive there, so the Builders built Ember. They knew, however, that someday the light in Ember would be extinguished, so they made instructions to leave Ember. Those instructions were put in a box, and the box was set to open in 200 years. It was passed down from mayor to mayor, until one day, while it was stored in a closet, the box slowly clicked open.
Now, Lina is worried about Ember. The lights are struggling to stay on, and sometimes they black out, and nobody knows if they will come on again. The food is running out, too. It has been that way for years. Lina is running out of hope, until one day, she finds her little sister, Poppy, tearing some paper. Lina steals it back from her, and tries to piece all the tiny scraps together. Could these papers be their way out of Ember? Doon, one of Lina's friends, helps Lina on an adventure to cover the mystery that has hidden for decades.
This was a very good book, especially if you like dystopian type things. (Dystopian is books about the future, usually ruled by some sort of society; Hunger Games, Legend, etc.)