The war of the e-book readers heated up Monday when Target Corp. said it will be the exclusive U.S. retailer for the first device that accesses the Google e-book library via Wi-Fi.

Target will have a six-month exclusive on the Story HD, which will compete head-on with the Barnes & Noble Nook, Amazon Kindle, Sony Reader and more than 70 lesser-known e-book readers.

The Target e-reader, from the California company iriver, costs $139.99 and will be available in stores beginning Sunday.

Target didn't return a phone call about the e-reader, but Google and iriver were eager to talk about it. Executives from those companies said the Story HD offers Wi-Fi connectivity to Google's online bookstore, along with a sharper screen image and quicker page changes than competitors.

While there are established competitors, the two companies say that e-books are so popular that there are enough customers for everybody.

"We're going after new buyers," said Pratip Banerji, product manager for Google e-books in Cambridge, Mass. "The market penetration of e-readers has only recently reached the double digits."

The book industry has been stunned by the e-book sales phenomenon. In March, e-book sales were up 145.7 percent from a year earlier, compared with 6 percent sales growth for adult hardcover books and a 7.7 percent sales decline for adult paperbacks, according to the Association of American Publishers.

A month later, the association reported that April e-book revenue totaled $72.8 million, compared with $111.4 million for adult hardcover books and $95.9 million for adult paperbacks.

But consumers who want to join the e-book revolution may be left scratching their heads about which e-reader to buy.

A selling point for the Story HD is that it can access the Google library via Wi-Fi. But you don't need the new e-reader to use the Google eBook Store, so long as you're willing to first download your e-book to a computer, then transfer it to a compatible e-reader by connecting cable.

Other top competitors also offer libraries similar to Google's. When it comes to popular new books and classics that most people read, Banerji said the Google, Amazon and Barnes & Noble libraries are probably about the same. Google offers an additional 3 million antique books that have long been out of print.

The Story HD doesn't have a touchscreen like the newest Nook model. Iriver says it may put out a touchscreen model later.

Owen Kwon, general manager of iriver Inc. in Irvine, Calif., said he believes that people are ready to join the e-book revolution.

"The e-reader market will be growing faster than ever for the next three to four years," Kwon said. "We're appealing to people who haven't tried an e-reader before, or who want something different."

Steve Alexander • 612-673-4553