The People of Sparks

Blurb

The People of Sparks, a post-apocalyptic science fiction novel by Jeanne DuPrau that was published in 2004. It is the second "Book of Ember" in the series, and a sequel to The City of Ember; other books in the series include The Prophet of Yonwood and The Diamond of Darkhold.
The Playtone Company also purchased the rights to The People of Sparks, but after the box office failure of the first film, plans for the sequel were shelved.