Wool: Book One of the Silo Series (Silo Series, Book 1) by Hugh Howey
 
The first book in the acclaimed, New York Times best-selling trilogy, Wool is the story of a community living in an underground silo completely unaware of the fate of the outside world. When the silo's sheriff asks to leave the silo, a series of events unravels the very fabric of their fragile lives. In a world where all commodities are precious and running out, truth and hope may be the most rare...and the most needed.