Genre: Children's Literature
Setting: Earth, two hundred years after the catastrophe. About two years after the people of Ember came to the surface.
First Sentence: Around the middle of the twenty-first century, when it seemed that a great catastrophe was about to engulf the world, an underground city was built as a last refuge for the human race.
This novel is the fourth in the author's "Books of Ember" series.
The builders of Ember realized that after two hundred years underground the Emberites would need to have some help restarting above ground life.
So the builders decided to give the people of Ember some help. Outside of the city they built a vault. In the value the builders placed a valuable piece of technology (the diamond) along with the instructions for using it.
Unfortunately, someone not of Ember discovered the technology first.
Meanwhile, life goes on in Spark. Spark is where the people of Ember and the People of Spark learned to live together.
Life is hard and dangerous. Eventually our main characters, Lena and Doon, are reminded of all of the things they had in Ember. They decide to return to Ember to see is there are any things left that might help the people of Spark.
They find that a family of roamers have taken up residence in the underground city. The roamers are using books from the library to fuel their fires. And they are looting the city for items they could use or sell.
Eventually, the roamers are chased off. Lina and Doon learn how to use the diamond. And, the people from Spark salvage what they can from the underground city.
With the items they recover from Ember, life becomes a little bit easier.
In the end the author provides a wistful happy ending, and a tie-in to the third book of the series. It is a weak and unimportant connection.
I liked this book. It is very much like the first two. I suggest reading the books in order.
P.S. I keep thinking about all of the boats the Emberites used to escape from Ember. They could have made a killing in the boat business!