Just finished reading Wool (1-5 Omnibus edition) and the subsequent prequel First Shift by Hugh Howey. Wow what a series. I recommend you all read it (if you're the reading type). For the love of all that is holy in this world do not read First Shift before you've read wool. But do read them.
Wool is set in a post apocalyptic underground self sustaining city, called a 'silo' where what remains of humanity struggle to survive. I really can't say more without ruining one part or another so I'll just leave it at that.
You can buy each wool book for $0.99 as kindle ebooks, except I believe 5 is more expensive, but its at least 3 times as long as the first book. I bought 1-5 in one big ebook for $5.99. Worth. Every. Penny.http://www.amazon.com/Wool-Omnibus-Edition-ebook/dp/B0071XO8RA/ref=pd_sim_kstore_1?ie=UTF8&m=AG56TWVU5XWC2