Amazon introduced the Kindle DX on Wednesday, expanding the ebook reader lineup with a bigger screen and native PDF support. The Kindle DX sports a 9.7-inch electronic paper display and storage for up to 3,500 electronic books.

Like the smaller 6-inch display Kindle 2, the Kindle DX includes a built-in keyboard, wireless downloads via the 3G Amazon Whispernet network, and text-to-speech support.

Amazon is targeting education and research with its new Kindle model. Educational book publishers Cengage Learning, Pearson, and Wiley have already committed to offer text books  through the online Kindle Store, and the New York Times and Boston Globe plan to offer special subscription rates for Kindle owners, too.

With the Kindle 2 offering a 6-inch display, Amazon's Kindle for iPhone application, and now the Kindle DX, Amazon is in a strong position to be the top player in the ebook market space.

The Kindle DX is priced at US$489 and is available for pre-order now. It is expected to ship some time this summer.