The City of Ember by Jeanne DuPrau
Lina and Doon live in the city of Ember, a dark city that is brightened by the great lights. When the lights start to flicker, will Lina and Doon be able to save the city, or will Ember fall into endless darkness?
This book is filled with such adventure, it's hard to put down. Once you finish, the cliffhanger at the end of this book will make you want to read more of the Book of Ember series!