Online retailing giant Amazon.com announced on Monday that it has already sold "millions" of the recently released Kindle Fire tablet computing devices and Kindle eBook readers, immediately establishing the Fire as the only viable alternative to Apple's successful iPad. Analysts now expect Amazon to sell several million units through the end of the year.

Amazon has always been vague about sales of its Kindle devices, though market researchers say the device is the dominant player in the ebook reader market. With the Kindle Fire, Amazon has extended its Kindle lineup to include a general-purpose computing device that looks and works much like the iPad but costs dramatically less. And Amazon says the device is selling fantastically well. It just won't say how well.

"Even before the busy holiday shopping weekend, we'd already sold millions of the new Kindle [devices], and Kindle Fire was the best-selling product across all of Amazon.com," the company noted in a press release tied to the "Black Friday" shopping event last week. "Black Friday was the best ever for the Kindle family: Customers purchased four times as many Kindle devices as they did last Black Friday. In addition, we're seeing a lot of customers buying multiple Kindles—one for themselves and others as gifts. We expect this trend to continue ... through the holiday shopping season."

Kindle Fire is the best-selling item on Amazon.com, the company noted. It costs only $199—far less than the $665 average selling price of the Apple iPad. In fact, you could purchase three Kindle Fires for the price of one mid-level iPad.

And it's not just successful on the web: The Kindle Fire is apparently (ahem) on fire wherever it's sold. A representative of the brick-and-mortar retailer Target stated that the Kindle Fire was the chain's "bestselling tablet." And electronics giant Best Buy noted that the Kindle Fire would "only get hotter as we get into the shopping season."

The Kindle Fire is part of a wider family of Kindle devices, most of which are e-ink based ebook readers. This holiday season, Amazon refreshed its line of devices, adding a new, low-cost Kindle device for just $79 and a multi-touch version, the Kindle Touch, which starts at $149. I've provided an overview of this device lineup and reviewed all of these devices on the SuperSite for Windows:

Amazon Kindle Fire
Amazon Kindle Touch
Amazon Kindle (Base Model, 2011)