Online retailing giant Amazon this morning announced its third-generation Kindle eBook reader, which is smaller, lighter, and faster than its predecessor, while offering the same screen dimensions and 50 percent better contrast. Best of all for potential customers, the new Kindle is getting a significant price cut, with the base model costing just $139.

For this generation of the Kindle, Amazon is offering two versions: a 3G + Wi-Fi model with free 3G wireless connectivity and international wireless coverage that costs $189, as before, and a new $139 Wi-Fi model that eschews those features. They join the larger Kindle DX, which features a 9.7" screen and costs $379. (The Kindle DX is targeted at the educational market.)

"Readers are going to do a double take when they see Kindle's bright new screen and feel how remarkably light the smaller design feels in one hand," said Amazon Founder and CEO Jeff Bezos. "If you don't need the convenience of 3G wireless, we have an incredible new price point—$139 for Kindle Wi-Fi. Kindle Wi-Fi has all the same features, same bookstore, same high-contrast electronic paper display, and it's even a tiny bit lighter at 8.5 ounces. "

The new Kindle ships August 27 and is Amazon's latest response to Apple's iPad, a tablet-shaped PC-like device that offers eBook functionality as well as other features. But the iPad starts at $500, and its average selling price of $630 is more than four times the price of Amazon's devices. Also to the Kindle's advantage are its dramatically better battery life (1 month vs. the iPad's 10 hours), far lighter weight and smaller size, and superior screen—which isn't reflective and offers excellent contrast for reading. And the Kindle benefits from a vast media library that the iPad can't match, where most Kindle eBook titles are cheaper than on the iPad.

The new Kindle also undercuts other dedicated eBook readers, such as the Sony Reader, at least for now. Sony's cheapest model, the Reader Pocket Edition, costs $150 but doesn't offer any Wi-Fi functionality.

What Amazon isn't offering, yet, are touch capabilities and color screens. The two technologies "aren't ready for prime time," according to Bezos, not for eBook reading. But the company promises both technologies in a future version.