Amazon.com on Monday launched an e-book reader that wirelessly downloads, books, newspapers, magazines and other digital content from the online retailer's store.

Called Kindle, the portable reader weighs slightly more than 10 ounces, and has a high- resolution, 6-inch diagonal electronic paper display that Amazon says reads like real paper, even in bright sunlight. The device is slightly more than a half-inch thick.

More than 90,000 books are available in Amazon's Kindle Store, including most current New York Times Best Sellers. Most books are priced at $9.99, and monthly subscriptions for newspapers run from $5.99 to $14.99, magazines from $1.25 to $3.49, and blogs for 99 cents each. The reader costs $399.

Amazon has been working on Kindle for more than three years. "Our top design objective was for Kindle to disappear in your hands -- to get out of the way -- so you can enjoy your reading," Jeff Bezos, Amazon.com founder and chief executive, said in a statement. "We also wanted to go beyond the physical book."

In doing the latter, Amazon decided to design the reader so the user can buy content from the device, without having to connect to a home computer. The device's wireless delivery system, called Amazon Whispernet, uses the same nationwide high-speed data network EVDO as advanced cellular phones. Amazon pays for the wireless connectivity, so there are no monthly bills for the download service, which can deliver books in less than a minute.

The device has built-in access to The New Oxford American Dictionary and online encyclopedia Wikipedia.org. It also has a standard-layout keyboard for searching the online store and stored content, and for adding annotations to text and for book-marking pages for future use. The device requires a battery charge every other day, if the wireless connection is left on. With the connection turned off, the reader can run for a week without recharging the battery.

Users can e-mail pictures and Microsoft Office Word documents to their Kindle e-mail address for 10 cents each. Kindle supports Word, HTML, TXT, JPEG, GIF, PNG, and BMP files. It does not support Adobe's popular PDF document format.

In launching its new e-book reader, Amazon follows by about a month and a half Sony's introduction of a similar device. The latter Reader Digital Book does not have a wireless connection, but costs nearly $100 less.

Other rivals in the e-book market include iRex Technologies, which makes the iLiad. The device has a touch screen that enables the user to make notes with a stylus, and includes a Wi-Fi connection. The iLiad costs $699.

Most e-book readers use a display technology called E Ink in their high-contrast screens. The technology is licensed from E Ink Corp. The devices in general are considered a niche market attractive mostly to avid readers. For that to change, analysts say, prices for the device will have to come down considerably.