Shares of Barnes & Noble fell on Friday after the company said it was cooperating in a Securities and Exchange Commission investigation into its accounting.

The SEC told the bookseller Oct. 16 that it was investigating the company's restatement of earnings announced in July as well as an employee allegation that it improperly allocated some information-technology expenses between its Nook and retail segments, according to a filing made after the market closed Thursday.

Barnes & Noble has been working on a turnaround in the face of tough competition and customers increasingly choosing digital books, music and video.

Shares fell $1.23, or 7.5 percent, to $15.16 in midday trading. The stock is up about 9 percent since the beginning of the year.