Electronic books accounted for 282.3 million dollars of sales in the first quarter of 2012 (up 28.1 percent from year), according to the Association of American Publishers (AAP).
It's the first time that e-book sales account for more than hardcover books, sales of which accounted for $229.6M, (up 2.7 percent from last year).
Paperbacks remain the most lucrative sector, with sales totaling $299.8M, but they registered a drop of 10.5 percent compared to last year.
Another figure reinforces the trend: exports of American books reached $357.4M (up 7.2 percent). While the portion of electronic books in that total remained relatively minor at $21.5M, it showed an increase of 332.6 percent in one year.
This data was based on sales figures from 1,189 publishers and does not include data for children's books.