"Kindle, already the number-one best-selling, most-wished-for, and most gifted product on all of Amazon.com, is now even better -- with 85 percent more battery life and a built-in PDF reader," said Ian Freed, vice president of Amazon Kindle. "These two significant enhancements are available now."

Upgrading Older Kindles

As Freed mentioned, the six-inch Kindle now has a built-in native PDF reader that lets Kindle users read professional and personal documents in the original PDF format without conversion.

Kindle users who want to read personal or professional PDFs can e-mail them to their Kindle e-mail address, or move them over using a USB stick. Customers who prefer to have their PDF documents converted to the Kindle format can type "convert" in the subject of the e-mail when sending documents to their "@kindle.com" address.

Amazon also announced Tuesday that previous purchasers of the Kindle will also receive the battery-life improvements and native PDF support via a firmware update automatically delivered through Whispernet wireless.

Assessing the E-Reader Wars

"We are in the early days of the e-book reader wars and companies are looking to differentiate themselves. Amazon has over a year's head start with its next generation of devices," said Michael Gartenberg, a vice president at Interpret. "Maybe the best reason I can think of for buying a Kindle if you are in the market for an e-book reader is because the Kindle has got availability and everyone else doesn't yet."

Gartenberg referred to shortages of Barnes & Nobles' nook and Sony's Reader Daily Edition. But even with its competitors short-handed, Amazon isn't resting on its laurels. The company is moving to ensure consumers in the market for an e-book reader choose the Kindle this holiday shopping season.

"Amazon does realize they are not the only game in town at this point. They've started to do TV commercials, which is something we've never seen them do with this product in the past," Gartenberg said.

"Right now you've got all the big players in the game on the book side of the equation, and on the publishing side. We've got Sony in the game. We keep hearing persistent rumors of Apple doing some sort of device in this category. It's a rumor that doesn't seem to want to die," Garenberg said. "It will be interesting to see [what] the next crop of devices look like and how consumers embrace them, or don't embrace these devices, next year."