New York City — Elliott Management Corp. has agreed to acquire Barnes & Noble for $683 million, or $6.50 per share. In 2014, Barnes & Noble closed its New York Fifth Avenue store, which was once the world’s largest bookstore. The company operates 627 stores in all 50 states. Elliott, which acquired the U.K.’s largest book retailer, Waterstones, last year, will become the largest bookseller in the U.S. when the acquisition is finalized. The deal is expected to close by the end of September. Barnes & Noble has been exploring options for a buyout since at least last October, with multiple parties showing interest, including founder-chairman Leonard Riggio. Riggio acquired the flagship Barnes & Noble trade name in the 1970s, nearly a century after Charles Barnes started the business in his Illinois home.