Lagardère SCA, the company that owns the Hachette Book Group, announced its third quarter revenues today, and reported that its digital book business continues to grow.

According to the company, eBooks now represent 21% of HBG’s net sales, which is up from 9% of net sales for Q3 2010. This is a 134% growth over total eBook sales in 2010.Bestsellers helped contribute to these sales as Hachette on the New York Times’ new eBook bestseller list.

According to the press release, eBook sales helped the company, since net sales in English-speaking countries during the quarter. Net sales fell 8% in the US and 10% in the UK which the company attributed to the impact of lower margins from eBooks and retail bankruptcies such as Borders going out of business.