By some measures, Barnes & Noble’s retail business may be worth nothing as the overall company is valued at around $863 million and its total enterprise value is about $1.3 billion, according to S&P’s Capital IQ. In fact 2012, Microsoft and Pearson bought a 23 percent chunk of the Barnes & Noble’s Nook division at $1.8 billion valuation. Surely, Barnes & Noble has nearly 700 stores and an e-commerce business, and according to the Wall Street Journal, its chairman Leonard Riggio says he’d buy the retail unit and he would likely need to value the business at about $1 billion, based on multiples tied to its earnings before interest, taxes, depreciation and amortization. That value would include the $338 million in debt, while And Riggio himself is owed $127 million in notes from a 2009 transaction involving the company’s college book stores unit. That would leave a $534 million hole to the total value.