Barnes & Noble, the giant that helped put so many independent booksellers out of business, now finds itself locked in the fight of its life. Its engineers dreamed up the Nook, a relative e-reader latecomer that has nonetheless become the great e-hope of Barnes & Noble and, in fact, of many in the book business.

Several iterations later, the Nook and, by extension, Barnes & Noble, at times seem the only things standing between traditional book publishers and oblivion.

Inside the great publishing houses — grand names like Macmillan, Penguin and Random House — there is a sense of unease about the long-term fate of Barnes & Noble, the last major bookstore chain standing. First, the megastores squeezed out the small players. (Think of Tom Hanks’s Fox & Sons Books to Meg Ryan’s Shop Around the Corner in the 1998 comedy, “You’ve Got Mail”.) Then the chains themselves were gobbled up or driven under, as consumers turned to the Web. B. Dalton Bookseller and Crown Books are long gone. Borders collapsed last year.

No one expects Barnes & Noble to disappear overnight. The worry is that it might slowly wither as more readers embrace e-books. What if all those store shelves vanished, and Barnes & Noble became little more than a cafe and a digital connection point?