Except for erotica, readers like to flaunt their taste.

BINDU WILES WAS on a subway train in Brooklyn in March when she spotted a woman reading a book whose cover had an arresting black silhouette of a girl’s head set against a bright orange background.

Ms. Wiles noticed that the woman looked about her age, 45, and was carrying a yoga mat, so she figured that they were like-minded and leaned in to read the title: “Little Bee,” a novel by Chris Cleave. Ms. Wiles, a graduate student in nonfiction writing at Sarah Lawrence College in nearby Bronxville, tapped a note into her iPhone and bought the book later that week.

Such encounters are becoming increasingly difficult. With a growing number of people turning to Kindles and other electronic readers, and with the Apple iPad newly arrived, it is not always possible to see what others are reading or to project your own literary tastes.

You can’t tell a book by its cover if it doesn’t have one. “There’s something about having a beautiful book that looks intellectually weighty and yummy,” said Ms. Wiles, who recalled that when she was rereading “Anna Karenina” recently, she liked that people could see the cover on the subway. “You feel kind of proud to be reading it.” With a Kindle or Nook, she said, “people would never know.”


MICHAEL NAGLE FOR THE NEW YORK TIMES
In public places, book covers can catch the eye of a potential reader or convey some insight into its owner’s taste. But e-readers like the Kindle send a blander message.

MARK LENNIHAN/ASSOCIATED PRESS


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.

“So often when you’re thinking of a book, you remember its cover,” said Jeffrey C. Alexander, professor of cultural sociology at Yale University. “It’s a way of drawing people through the visual into reading.”

In the bookstore, where a majority of sales still take place, covers play a crucial role. “If you have already passed that hurdle of having a customer be attracted to the cover, and then they pick up the book,” said Patricia Bostelman, vice president for marketing at Barnes & Noble, “an enormous battle has been won.”

But it’s a victory that will be harder to eke out if no one can tell whether you’re reading “War and Peace” or “Diamonds and Desire.”

Perhaps no other element of the book-making process receives as much input from as many different people as the jacket. First, a creative director comes up with an idea. (How about this image of an apple?) Then the book’s editor, author and agent have a look. (Can we enlarge the font size on the author’s name? And wasn’t an apple used for that book about vampires? This book isn’t about vampires.) The publisher gets involved. (Vampires sell. I like the apple.) The sales force makes comments. (How about an apple with an orange inside? That’s worked before.) Even booksellers have an opinion. (What I really love on a cover is a pair of high heels.)

A good jacket is unlikely to save a bad book, of course. But in a crowded market, a striking cover is one advantage all authors and publishers want. To get a sense of the odds, in a random analysis of 1,000 business books released last year, Codex Group, a publishing consultant, found that only 62 sold more than 5,000 copies.

As publishers explore targeted advertising on search engines or social networking sites, they figure that a digital cover remains the best way to represent a book.

Some readers expect makers of electronic devices to add functions that allow users to broadcast what they’re reading. “People like to show off what they’re doing and what they like,” said Maud Newton, a popular book blogger. “So eventually there will be a way for people to do that with e-readers.”

For now, many publishers are counting on the Facebook effect. “Before, you might see three people reading ‘Eat, Pray, Love’ on the subway,” said Clare Ferraro, president of Viking and Plume, imprints of Penguin Group USA. “Now you’re going to log onto Facebook and see that three of your friends are reading ‘Eat, Pray, Love.’ ”

Some digital publishers suspect that one of the reasons romance and erotica titles are so popular in electronic editions is because e-readers are discreet.

Book jackets, though, still matter.

Holly Schmidt, president of Ravenous Romance, an e-book publisher of romance and erotica, said that in one case the publisher was offering an anthology of stories about older women and younger men. The first version featured a digital cover image of a winsome woman. It barely sold any copies. The publisher put a new cover up online - this time showing the bare, muscular torsos of three young men - and sales took off.

The new cover “took a book that was pretty much a loser,” Ms. Schmidt said, “and made it into a pretty strong seller.”


RUTH FREMSON/THE NEW YORK TIMES
Publishers lose free advertising as covers disappear. Asiria Mateo read the novel “Deep” on the subway.