Amazon.com's net sales increased 22% to $21.27 billion in the fourth quarter, 2012 compared with $17.43 billion in fourth quarter, 2011.

Operating cash flow increased percent to $4.18 billion for the trailing twelve months, compared with $3.90 billion for the trailing twelve months ended December 31, 2011. Free cash flow decreased 81 percent to $395 million for the trailing twelve months, compared with $2.09 billion for the trailing twelve months ended December 31, 2011.

Net income decreased 45% to $97 million in the fourth quarter, or $0.21 per diluted share, compared with $177 million, or $0.38 per diluted share, in fourth quarter 2011.

"We're now seeing the transition we've been expecting," said Jeff Bezos, founder and CEO of Amazon.com.

"After 5 years, eBooks is a multi-billion dollar category for us and growing fast - up approximately 70 percent last year. In contrast, our physical book sales experienced the lowest December growth rate in our 17 years as a book seller, up just 5 percent. We're excited and very grateful to our customers for their response to Kindle and our ever expanding ecosystem and selection," commented Jeff Bezos.