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.

For the quarter, sales were up in seven of the 14 categories tracked by AAP with the strongest gains among print segments coming in trade paperback, with sales up 23.5%, and higher education where sales increased 18.3%. Sales in the children’s/young adult hardcover segment fell 35.2% in the quarter, while paperback sales in the category were down 8.6%.