I am amused by the review that calls this book "The Prophet of Yawnwood", and unfortunately I agree. I was pretty disappointed by this third book in the Ember series. The first book is excellent and the second is still interesting; this one is just dull and preachy. Worse than that, the story is only tangentially related to the rest of the series, so much so that I have a hard time even calling it a prequel. 
 The setting (a major strength in the rest of the series) is pre-apocalypse and sadly unremarkable. Even without comparing to the other Ember books, the book is pretty weak on its own. The protagonists are unrealistic children. The villains aren't that scary. (view spoiler)[If you obey them, they don't let you sing and set your dog free in the woods. If you disobey, they make you wear a noisy wristwatch! (hide spoiler)] Mysteries are introduced, but ultimately just remain mysterious, and do not clearly lead to the fascinating, yet never explored, creation of Ember. I have to admit that the cover is pretty cool though. 
 I look forward to returning to Lina and Doon's story in The Diamond of Darkhold.