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Via Publishers Weekly:

E-books accounted for 7% of consumer spending on books in 2011 and 14% of units purchased, according to the most recent data from Bowker Market Research. In 2010, e-books had a 2% share of dollars and a 4% share of units. The wide discrepancy between unit and spending gains reflects the lower price e-books have compared to print formats, especially hardcover. The increase in spending on e-books came largely at the expense of hardcover, with the market share for hardcovers falling from 42% in 2010 to 39% last year. In 2009, hardcovers held a 46% share of spending. Unit sales of hardcovers took a slightly steeper drop last year, falling from 34% of titles sold to 29%. Trade paperback fared better, with the Bowker data showing that after holding steady at 36% of spending in 2009 and 2010, trade paperback accounted for 37% of spending last year despite a dip in its share of units. The mass market paperback segment has had a steady decline in units and dollars between 2009 and 2011, with units falling from 18% in 2010 to 14% in 2011; its share of spending fell last year

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