What if the long-term survival of the human race depended on thousands of Americans being relocated to a vast underground city, with giant TV screens broadcasting a desolate landscape outside and no one allowed to leave?

SHIFT, by Hugh Howey. Arrow, 2013, 608 pp., $20.99 (paperback)

That was the idea behind "Wool," the series of short stories Hugh Howey began selling online for between 99 cents and $2.99 in 2011, and which overtook "Game of Thrones" last summer on online retailer Amazon's list of sci-fi best-sellers. Print and film deals followed, as did this prequel, made up of three interweaving stories sold cheaply by Howey through Kindle Direct Publishing and then packaged and printed as a full-length novel. (In the U.K. they were picked up by the same imprint behind "Fifty Shades of Grey.")