Yet another Kindle model has been introduced by Amazon. The Kindle 2 was launched on February 9, with a 6-inch screen (roughly the size of a mass-market paperbook). The new Kindle DX has a 9.7 inch screen. According to Amazon’s Jeff Bezos, the DX is perfect for college students reading textbooks and business professionals reading documents. The DX has a built-in PDF reader, allowing readers to access the thousands of volumes available on Google Books. With a weight of 19 ounces, the DX is engineered to not feel big and bulky. The thing that is big is the cost — at $490, it’s the costliest Kindle to date.