Barnes & Noble says its loss more than doubled in the latest quarter as its Nook e-book reader unit continued losing money and sales plummeted at its bookstores.

The largest traditional U.S. bookseller has invested heavily in its Nook devices and digital library to beat back competition from online retailers and discounters, but the unit has yet to turn a profit.

To limit its manufacturing risks and reduce losses, Barnes & Noble Inc. now says it will work with a yet-to-be-announced third party to make its tablets.

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For the quarter, the company said it sold fewer Nook devices and that sales of digital content for the readers also fell 9 percent. The company blamed in the decline partly on the tough comparison from a year ago, when "The Hunger Games" and "Fifty Shades of Grey" trilogies boosted results.

At its bookstores open at least a year, it said sales fell 8.8 percent during the period. It also warned it expects that figure to decline in the "high-single digits" for its fiscal 2014. The figure is a key metric because it strips out the impact of newly opened and closed locations.

Overall retail sales, which include Barnes & Noble bookstores and online sales, declined 10 percent in part because of store closures.

The company also said it's reviewing financial statements that may result in a revision. Its stock was down 8 percent at $17.36 in premarket trading.

For the February to April quarter, Barnes & Noble Inc. said its net loss totaled $118.6 million, or $2.11 per share. That compares with a loss of $56.9 million, or $1.06 per share, last year.

Revenue fell 7 percent to $1.28 billion.

Analysts expected a loss of 97 cents per share on revenue of $1.33 billion.

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