Successful childrens’ books publisher Nicholas Callaway believes paper is dead and that digital has come of age, writes Mark Egan. But Callaway isn’t worried that big publishing houses will eat his lunch. “They don’t understand the new medium, they don’t have the rights, they don’t know how to create the product and they don’t know how to get it out to the world,” Callaway told Egan. January e-book sales more than doubled from the same month a year earlier, rising 116 percent to $69.9 million, according to the Association of American Publishers. That topped sales of hardcover books, which fell 11 percent from January 2010 to $49.1 million.