Sales of ebooks more than doubled in 2011 to bring in some $2.07-billion for the US publishing industry, a survey showed on Wednesday.
The data from the Association of American Publishers and the Book Industry Study Group said ebooks grew from $869-million in 2010. Last year, ebooks accounted for some six percent of overall publishing revenues.
The number of ebooks also doubled to 388 million, and represented 15.5 percent of total books sold in the "trade sector," meaning fiction and non-fiction for adults and children.
Still, ebooks have not overtaken the traditional hardcover or paperback, which represented the bulk of publishers' net revenue at $11.1-billion for 2011.
The biggest gains for ebooks came in adult fiction, where it accounted for 30 percent of revenues. That was up 117 percent and produced $1.27-billion in revenues last year, the report said.
Overall sales for the publishing industry managed a slight increase for the year of 0.5 percent at $13.97-billion.
And despite the bankruptcy of the big bookseller Borders, which closed 500 stores, brick-and-mortar retail remained the top sales channel with $8.59-billion in sales.