Lina is 12 years old, and in Ember, that means she starts her job. What she wants is to be a Messenger - taking messages throughout the city of Ember, running, free... What she gets is Pipeworks - underground, wet and something she dreads. Only her friend Doon switches with her. Ember is a city totally reliant on artificial lighting and the system is falling apart and supplies are running low. Lina finds scraps of a message that portents a way out and she and Doon set out to see whether they can find the way out. 
 Though the characters are quite young, they are smart and resourceful and this is an engaging story and I really enjoyed it. Look forward to reading the next in the series.