Kindle DX is a nifty, if costly, way to carry your library

— -- Avid readers usually have a choice. Read a current hardcover best seller that's heavier to travel with and more expensive. Or lighten the load with a cheaper paperback whose title is dated.

At 18.9 ounces, the DX still weighs less and is much thinner than most hardcover books. As with previous Kindles you can cart a whole library. The DX stores up to 3,500 books, compared with 1,500 for its paperback-size sibling, the Kindle 2. But Kindle 2 is about a half-pound lighter. Both models fit into a knapsack with no problem.

There's a weightier consideration: cost. At $489, the DX commands a premium that's hard to justify, especially in this economy. I'm a fan of Kindle 2, but even it is too pricey at $359.

What's more, the students who represent a prime potential market for the DX — Amazon is making a push on college campuses and with textbook publishers — may be cash poor.

Amazon says ardent readers can recoup the cost eventually, because books sold in the wireless Kindle Store are discounted, $9.99 for most best sellers.

It's still mostly unknown, though, what textbook publishers plan to charge. The one I sampled, Biology of Fishes by Richard H. Moore, costs $68.80 in the Kindle Store, down from the $86 digital list price. I'd expect decent price breaks. Physical textbooks are often resold as used books, so publishers get bupkis.

Why consider a Kindle DX? The obvious answer is the larger screen, 9.7 inches. All models are based on the same black-and-white E-Ink technology that does such a fine job of mimicking the experience of reading on paper. But the DX has 2½ times the surface area, making it better suited for textbooks, newspapers and magazines.

Another plus: The DX can handle business and personal documents in the Adobe PDF format; these must be converted before you can read them on Kindle 2.