I had just finished the Wool Omnibus series, which had left me in one of those reeling, reflective, happy book-stupors that only really good stories can leave you with. Then I see that there is a follow-up, a prequel no less? Say what? I read it immediately of course. 
 (view spoiler)[First Shift answers your questions about what happened to the world, how did these silos get here, and what's the deal with Silo 1. (hide spoiler)]