Amazon has just announced that its Kindle ebook reader is out of stock. The electronic book reader won't be available until February. This will mark the second Christmas sell-out for the wireless reader device, as the online retailer once again underestimated the demand for the ebook reader. Recent demand soared in October, when Oprah Winfrey praised the Kindle wireless reader, calling it her favorite gadget. After this moment, Kindle started disappearing off store shelves and Amazon did nothing to prevent this from happening.

The ebook reader costs $359 and it offers a free Wi-Fi connection, where users can preview or purchase electronic books, which can be auto-delivered in less than one minute. Amazon offers about 200,000 different titles available for digital download. A couple of weeks ago, Bertelsmann AG's Random House, the largest publisher of consumer titles in the U.S., announced that it will convert more than 6,000 additional titles to e-books, bringing its total to nearly 15,000.

However, this is not the only electronic reader on the market. Sony' Reader, launched in the U.S. more than two years ago, is now in its third incarnation. The Sony PRS-700, priced at $400, comes with a touch screen, a built-in light, highlighting and annotation capabilities. Anyway, a simpler model, the PRS-505, is available for only $300. Many other handheld devices enable their owners to read e-books, including Apple's iPhone, which runs a free application, Stanza. In addition, the iRex, by iRex Technologies, is aimed at business users as a more portable way to read PDF files.