Barnes & Noble Inc. shares fell Thursday after the retailer said that it expects losses from its Nook e-reader business to be larger in 2013 than last year.

The largest traditional U.S. bookstore has invested heavily in its Nook business as consumers increasingly shop online and read e-books. But the Nook faces tough competition from other devices like Apple's iPad Mini, Amazon's Kindle and Google's Nexus tablet.

Barnes & Noble said Wednesday after the market closed that it expects Nook media revenue of less than $3 billion. It also anticipates a loss for the unit from earnings before interest, taxes, depreciation and amortization to exceed the $262 million loss recorded in its 2012 fiscal year.

This follows a report from the retailer in January that its Nook unit revenue fell 12.6 percent to $311 million during the critical holiday period.

The company is scheduled to report its third-quarter results on Feb. 28.

Shares sank 93 cents, or 6.6 percent, to $13.27 in midday trading Thursday. Its shares have traded between $10.45 and $26 in the past 52 weeks.