"The Association of American Publishers (AAP) has today released its annual estimate of total book sales in the United States. The report, which uses data from the Bureau of the Census as well as sales data from eighty-six publishers inclusive of all major book publishing media market holders, estimates that U.S. publishers had net sales of $23.9 billion in 2009, down from $24.3 billion in 2008, representing a 1.8% decrease. In the last seven years the industry had a compound annual growth rate (CAGR) of 1.1%."
"Audio book sales for 2009 totaled $192 million, down 12.9% on the prior year, CAGR (compound annual growth rate) for this category is still healthy at 4.3%. E-books overtook audiobooks in 2009 with sales reaching $313 million in 2009, up 176.6%" (http://www.publishers.org/main/PressCenter/Archicves/2010_April/BookSalesEstimatedat23.9Billionin2009.htm)