eBook sales grew a dramatic 164.8 percent in December 2010 to $49.5 million versus $18.7 million in December 2009, according to The Association of American Publishers.

On an annual basis, eBook sales were up 164.4 percent to $166.9 million for 2010 versus $441.3 million in 2009. In 2010, eBook sales represented 8.32 percent of the trade book market versus 3.20 percent the previous year.

Digital audiobooks did well as well. In December 2010, downloaded audio books increased 56.7 percent to $8.9M and physical audio books increased 34.5 percent to $15.8M. Sales for downloaded audio books rose by 38.8 percent to $81.9 million in 2010, versus $59.0 million in 2009, while physical audio books fell 6.3 percent to $137.3M for 2010 from $146.5M for the previous year.