The device itself isn’t very different than the old Kindle. But it explains where Amazon sees itself expanding.

At first, they hyped it as just a new way to read books. Then, three months ago, Amazon (AMZN) CEO Jeff Bezos paced the stage to announce the second-generation of the Kindle. Its primary purpose, too, was to read books. Sure, it could also deliver blogs, magazines, and newspapers, but just like Amazon's original business model for its Web site, the Kindle would focus on books first and expand from there.

Wednesday, Bezos was back onstage to announce a new incarnation of the Kindle just three months after unveiling the previous one. The new device is called the Kindle DX—which gives the device the unfortunate and impersonal naming convention of both video games and cars—and it's meant to do a whole lot more than read books. It's a wunderdevice that can display textbooks, newspapers, and personal documents.

But couldn't the old Kindle do all of that too? Yes—but you wouldn't know it from today's debut. On paper, the big differences are that the Kindle DX is 4 inches larger than the one you bought last month and comes installed with a PDF reader. But that's not the point. The point is that Jeff Bezos wants you to do something different with it.

Here's the Amazon spin, paraphrased: With the PDF reader you can better scan all those documents you would otherwise print out and lug around with you. Since newspapers are printed on big pieces of paper in the analog world, they should be displayed on bigger screens in the digital one. Textbooks, with all their graphics, diagrams, and charts, wouldn't look any good on a 6-inch screen. But that 10-inch screen will really make the black-and-white images pop off the digital page.

For those extra 4 inches and a PDF reader, you'll pay $130 more for a DX than a regular second-generation Kindle—$489 total.

So why did Amazon bother? To make money, of course. The new features—though mockably sparse—offer subtle clues to Amazon's revenue plans for the next decade. Each of the DX's prospective growth areas needs either the PDF reader or a bigger screen to generate revenue. Here's how: