Chalk up another milestone for electronic books: Barnes & Noble Inc. says its Nook e-reading devices have become the company’s best-selling products ever.

The multichannel bookseller, No. 42 in the Internet Retailer Top 500 Guide, also says that it sells more digital books than physical books on the BN.com e-commerce site. In fact, consumers bought 1 million digital books on Christmas Day from Barnes & Noble.

Additionally, the retailer says its Nookcolor was the company’s top-selling gift of the holiday season. The retailer did not say how many of the devices it sold. Barnes & Noble introduced Nookcolor eight weeks before Christmas. The device enables customers to purchase interactive digital content via a color touchscreen.

“We have a large online book business at BN.com that’s been recently growing,” says William Lynch, the retailer’s CEO. “And the fact that e-book unit sales now exceed physical book sales through BN.com illustrates how quickly we’ve grown this exciting new business at Barnes & Noble.”

The announcement from Barnes & Noble comes shortly after Amazon.com, No. 1 in the Top 500 Guide, said the third generation of its Kindle electronic reader was the best-selling product in the company’s history.