Bezos: With ebook sales up 70% in 2012, Amazon has hit "transition" it expected

Amazon announced fourth-quarter earnings slightly below investor expectations Tuesday afternoon — but operating income, widely viewed by investors as an important measure of the company’s overall health, rose, driving shares up in after-hours trading.

Net income for the quarter was $97 million, or $0.21 per share, on revenue of $21.27 billion — compared to profits of $177 million on revenue of $17.43 billion a year ago. Operating income rose 45 percent to $405 million.