Operating income increased 56% to $405m.
Amazon has reported a 22% rise in its revenues to $21.27bn for the fourth quarter of 2012, compared to $17.43bn it reported for the corresponding quarter in 2011.
Amazon's net income, however, declined 45% to $97m, compared to $177m for the same period in the corresponding year.
Operating income increased 56% to $405m in the quarter, compared to $260m for the same period last year.
The company's operating expenses increased 22% to $20.86bn, including a 56% growth in investment on technology and content areas like movie-streaming rights.
Fulfillment costs increased to $2.26bn in the quarter, compared to $1.66bn for the same period in the corresponding year.
Amazon founder and CEO Jeff Bezos said: "We're now seeing the transition we've been expecting. After 5 years, eBooks is a multi-billion dollar category for us and growing fast - up approximately 70% 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%."
Amazon started selling several new Kindle devices towards the end of the year including the Kindle Fire HD tablets.
The company expects revenues to be in the range of $15bn and $16.6bn for the first quarter of 2013.
Analytics firm, Localytics, said Amazon is dominating the US tablet market with half of all Android tablets in the country being Kindle Fires or Kindle Fire HDs.