Starting February 13, you’ll see a new category in The New York Times bestsellers lists: e-books. Acknowledging the growing popularity of e-books, the Times said it spent the last two years creating a system to track e-book sales. “We’ve had our eye on e-book sales since e-books began,” said Janet Elder, editor of news surveys and election analysis, in The New York Times. “It was clear that e-books were taking a greater and greater share of total sales, and we wanted to be able to tell our readers which titles were selling and how they fit together with print sales.”