Sales of electronic books have turned lower in 2015 in a stark reversal following several years of spectacular growth, an industry group said Wednesday.

The Association of American Publishers released data showing e-book sales down 10 percent in the first five months of the year compared with the same period in 2014.

The latest figures showed US e-book sales -- excluding educational titles -- of $610 million.

The group said it was the largest drop since the beginning of the e-book market. The e-book market has been growing strongly, with the exception of a small drop in 2013.

Print sales this year also fell but at a much slower pace, dipping just 2.3 percent, the trade group said.

"In the early years of e-books, the percentage growth from physical books to digital books was rapid. Now that e-reading is fully integrated into a consumer's choice of options, the market has begun to stabilize," Tina Jordan, vice president of the publisher group, told AFP.

"Book consumers still find reasons to buy print and to consume content digitally every day. Publishers are committed to offering the public choices not just in what they read, but how they read."

The association follows monthly sales from 1,200 publishers and has tracked e-book sale since 2002.

Interest in e-books has been on a sharp upward trajectory over the past few years, but their share of the market has steadied in recent times, accounting for 22.8 percent of the market in 2014, according to the association.