E-book sales from the 13 publishers that report results to the Association of American Publishers’ monthly sales program rose nearly 252% in the first quarter of 2010, to $91 million, the association reported this morning. Growth actually slowed somewhat in March from the earlier two months, but sales still increased 184.8% to $28.5 million. The e-book gains were easily the biggest in the industry in both the quarter and March. The AAP added a new category in the month, downloadable audio, and sales from the 10 companies that reported results rose 32.5% in the quarter, to $16.4 million; March sales were up 29.3%, to $6.2 million. Sales of traditional audio were up 14.7% for the quarter and 8.6% for March.