The Kindle 2 electronic reader that Amazon is now shipping has a new read-aloud feature. And for authors and publishers, that's a potentially troublesome development. "It's a contractual minefield," says Paul Aiken, executive director of The Authors Guild. "Authors often give audio rights to one entity and e-books rights to another."

Amazon said that the next-generation Kindle, priced at $359, was already ranked the top seller on its Electronics page, just a little over two weeks after it had been launched on February 9.

"One of the great things about Kindle is it doesn't ever get hot," Amazon Vice President Ian Freed said in an interview at Amazon's downtown office here. That's important, Freed said, given that the company has one main goal with the Kindle--making the product as invisible to users as possible when they are reading.

Another big new feature is one that is impossible to see: the new Whisper Sync feature that will eventually let people read the same electronic book on multiple devices, including Kindles and cell phones. The cell phone option, like a controversial new text-to-speech feature built into the Kindle 2, is more designed for short bits of content than as the primary mode of reading, Freed said. A cell phone is good for those unexpected times where one has a few minutes to read, while text-to-speech is good for those who are right in the middle of a cliffhanger and have to get in the car or cook dinner.

The problem surrounding the first-generation Kindle, however, was that demand far surpassed supply. Just a short time after its announcement, the Kindle was listed as "sold out" on Amazon's site, a familiar sight when shopping for the device and one that prompted an apology by chief executive Jeff Bezos.