Sales of Barnes & Noble’s Nook eReader have been higher than expected, helping the company’s market share in digital books exceed its share of physical books just one year after it entered the eBook arena, the company said in its earnings today.

“Since launch, sales of Nook have been nothing short of spectacular and consistently above plan,” Barnes & Noble said in its earnings, adding that eBook sales are “accelerating week-over-week.”

One-quarter of all new Nook customers are new to the book retailer and Barnes & Noble members with the device have increased their spending by about 20 percent, said Barnes & Noble CEO William Lynch in a statement. The company did not break out Nook shipments or sales in its financial results.

The company also promoted Jamie Iannone, who has overseen Barnes & Noble’s online business, eBookstore and Nook apps since he joined the company one year ago. Iannone is now responsible for the Nook, its software, accessories and retail integration, as well as eBooks, digital content and third-party partnerships. John Foley is now overseeing the company’s website business.

The success of the Nook, which helped bring sales up more than 20 percent to $1.4 billion, was not enough to offset rising expenses and legal fees related to a lawsuit by activist investor Ronald Burkle, whose Yucaipa investment firm is waging a legal fight with Barnes & Noble’s board of directors.

The company swung to a loss of $63 million, or $1.12 per share, for the first fiscal quarter ended July 31 including legal expenses of $9.5 million related mainly to the Yucaipa litigation.

The company lowered its full-year guidance on anticipated legal costs from the Yucaipa lawsuit. The company now expects full-year net loss per share to be in a range of $0.25 per share to $0.65 per share. Excluding these legal costs, the company’s full-year earnings per share guidance remains essentially unchanged with previously issued guidance of $0.00 to a loss of $0.40 per share.