NEW YORK>> Shares of Barnes & Noble are tumbling after airing some ugly holiday sales numbers.

The beleaguered bookseller said late Thursday that comparable-store sales slid 6.4 percent during the crucial nine-week period ending Dec. 30.

Most retailers have strengthened digital operations and their sales have followed. At Barnes & Noble, however, online sales dropped 4.5 percent.

Amazon.com is winning over more people each year to its Prime membership program, at one point handing out trial memberships to 4 million people in one week this holiday. That’s proven devastating for Barnes & Noble, where overall holiday sales fell 6.4 percent, to $953 million. The Seattle-based Amazon has also opened 13 physical bookstores so far.

Consulting firm Bain & Co. says that Amazon should account for half of holiday 2017 holiday sales growth.

Barnes & Noble says trends of improving sales leading into November began to fade by December.

Shares of Barnes & Noble Inc. fell more than 14 percent, to $5.57 in afternoon trading. That was the lowest point since 1994.