The Association of American Publishers says e-book (electronic book), sales topped $12 million in June - up more than 150 percent from the same month last year.  Manufacturers of hand-held, digital book readers are also reporting healthy sales.  Online retailer says sales of its device, called the Kindle, have exceeded expectations since its release in 2007.  The wireless devices allow consumers to purchase electronic-books online and read them on a screen almost instantly.

E-book readers are thin, like a magazine, and can store hundreds of titles on a device smaller than most paper books.  They are also portable and allow readers to download books using a wireless Internet connection.  Some devices even have a feature that reads the story out loud.

Sales of both e-books and digital readers are rising as American consumers continue to demand products that fit their increasingly mobile, computerized society.

"I definitely would find it more convenient for myself if I had a whole bunch of books just on this little computer," says digital-reader owner Pauline Camden.

Online retailer says it stocks more than 300,000 e-book titles.  It charges about $10 each for best sellers and new releases in e-book form.  Hardback versions often cost much more.  

Some authors and publishers have moved to digital releases to save on the costs of producing a book, such as printing, delivery and storage. These costs account for more than 12 percent of the retail price of a traditional book.

Mystery novelist Debbi Mack's (author of Identity Crisis) books are sold in electronic form. She says digital publishing is a valuable tool for authors.

"I think that it provides a lot of opportunities for people to get old, out-of-print work back out on the market. If you can't find a publisher, but you know that you have a quality product, it gives you a means of doing that," she says.

But critics say e-books are not as engaging as traditional paper books.

Author Eugenia Kim's (author of The Calligrapher's Daughter) new novel is available in both formats. But she says she prefers the feel of a traditional book.

"There is something wonderful about the tactile act of turning a page," she says, "and having that whole business of having the story reveal itself as you turn a page. I think it comes from a childhood experience with books."

Others shun electronic book publishing.  Richard Peabody publishes poetry and short stories in traditional form only.

"I really think that some people just don't want to read on the screen. If you work all day and you read [computer] screens all day long, it's like the last thing you want to do," he says.

Meanwhile, technology corporations are already battling over who should own the digital rights to many books.  Amazon, Microsoft and Yahoo oppose a legal settlement giving rival Google the rights to millions of copyrighted titles.

The companies say the settlement could hurt competition in the e-book market as more consumers choose to use electronic readers.