In what appears to be a definitive strike in consolidating online book discovery under one virtual roof, Amazon announced Thursday afternoon that it acquired Goodreads for an undisclosed sum. The company’s headquarters are expected to remain in San Francisco with the deal set to close in the second quarter of 2013 subject to various closing conditions. Founded in 2006 by Otis Chandler, Goodreads boasts more than 16 million members — vaulting it ahead of Shelfari (which Amazon acquired in 2008), LibraryThing (in which Amazon has a stake after buying AbeBooks in 2008), and Bookish, which finally opened for business earlier […]