The People of Sparks by Jeanne DuPrau

The People of Sparks is the sequel to The City of Ember! Lina, Doon, and Poppy (Lina's little sister) were the first to make it out of Ember, the underground city. They went walking during daylight and found a hole in the ground! From the hole they found you could see all of Ember! Lina and Doon wrote a note and tied it to a rock along with the directions on how to get out and dropped it down the hole. In a few days everybody that lived in Ember was out! There were about 400 of them. They walked for a long time. Finally off in the distance they could see a little town. But...what they didn't know was that somebody in the town saw them too. The three council workers did not want more mouths to feed. The people of Ember were assigned the houses they would be staying in for the time being. The rest were put in the Pioneer Hotel. Some of the people had to work. The people of Ember got very little food. One person of Ember really wanted to leave. His name was Tick. Most people of Sparks wanted them to leave too. Torren was the first one who saw them. He had a brother named Casper. Casper was a roamer. His partner was named Maddy. They were going on a trip to an ancient city. Lina stowed away in a large crate in the back of the truck. Casper was going to the ancient city because he thought there was a treasure there. He thought he figured it all out but he didn't. The city with the treasure was Ember and the treasure was the people of Ember. As soon as Lina and Maddy found out they rode off on bikes. Then they met another roamer. They rode with him back to Sparks. Along the way they stopped in other old cities and looked in the houses for old things. Lina found things like a Monopoly board and a magnifying glass. When they got back to Sparks Doon told Lina they were to leave the day after that day and Lina got really mad. The people of Sparks had a weapon! When they were about to go to war the weapon blew up and a huge fire started. Torren got stuck in a tree that was on fire but Doon saved him. The people of Sparks called the fire brigade. Then everyone started helping put out the fire. Lina was the first of Ember to help then almost everybody else from Ember helped too! The only ones who didn't help were Tick and a few of his followers. There was a big meeting at the Pioneer Hotel the day after. The people of Ember were allowed to stay, except for Tick and his followers. They went out to the wilderness and tried to survive. The houses for the people of Ember were to be built behind the fields. From that day forward the People of Ember were to be referred to as the People of Sparks!