U.S. e-book sales have surpassed those of hardcover books for the first time, a publishing industry association is reporting. The Association of American Publishers said net sales revenue from e-books exceeded that of hardcover books in the first quarter of 2012 for the first time, mashable.com reported Sunday. Adult e-books brought in $282.3 million in the quarter, while adult hardcover book sales accounted for $229.6 million, the association said. The e-books total is a 28.4 percent increase from the same period a year ago, it said. And while paperback sales remained in the lead at $299.8 million for the first quarter, that\'s a decline from the $335 million in the first quarter of 2011, the report said. Research published by Pew in April found a strong correlation between the spike in sales of e-reading-capable devices such as tablets, smartphones and dedicated e-readers and e-book adoption over the holidays.