How do you judge a book by its cover if it doesn’t have one?
Among other changes heralded by the e-book era, digital editions are bumping book covers off the subway, the coffee table and the beach. That is a loss for publishers and authors, who enjoy some free advertising for their books in printed form: if you notice the jackets on the books people are reading on a plane or in the park, you might decide to check out “The Girl With the Dragon Tattoo” or “The Help,” too.