In terms of power use, the Kindle is quite the modest spender, so battery life isn't really a big deal. Since you'll always be reading it in front of an adequate light source, though, you might as well take advantage of it to replenish the reader's battery. That's exactly what the SolarKindle proposes.
Made by SolarFocus, it's a specialty case designed for the Amazon Kindle with a built-in solar charger and reserve battery. That way, you can keep recharging the reader while reading under sunlight, effectively putting back every ounce of energy you use up. If you're lucky, you may never have to charge your Kindle off a USB source again.
The SolarKindle is a folio-style reader case that measures 7.9 x 4.7 x 0.72 inches and weighs 7.58 ounces. Not exactly a showcase of good looks, it hosts a flexible solar panel on the front cover and a body decked in PU leather. It comes with a built-in 1,500mAh battery, which can replenish both via the solar panel or USB, acting as a reserve power source for the Kindle that can extend its usable life for up to 3 months without ever getting a sip from any other source. Exposure to one hour of direct sunlight can generate up to 3 days of nonstop reading time. And in case you decide to lock yourself up inside a dark cave for a weekend, you can keep up with your reading using the flip-out 800-lux LED lamp, which will draw power from the onboard case's battery for up to 50 hours straight.
Currently on exhibit at the floor of CES, the SolarKindle Lighted Cover will be available starting January 15th. Price is $79.99.