Yucaipa Cos., the investment firm of Los Angeles billionaire investor Ronald Burkle, has bought more than 4 million shares of Barnes & Noble Inc. doubling its stake in the New York bookseller to nearly 7 percent, according to a regulatory filing.

Yucaipa added the shares between Nov. 10 to 13, at an average price of $20.05, and now owns 9.6 million shares, according to the filing with the U.S. Securities & Exchange Commission.

Yucaipa in the filing called for better corporate governance at the company. “The reporting persons are concerned with the adequacy and enforcement of the company’s corporate governance policies and practices, as evidenced in part by the recent acquisition of Barnes & Noble College Booksellers Inc.,” the filing said.

Barnes & Noble last month warned that it expects to report a loss in its fiscal second quarter ended Oct. 31 in part due to expenses related to the $596 million acquisition of its managed college operations in September. The deal increases its number of stores at a time when the trend is moving toward digitization of college texts.

Barnes & Noble operates 774 retail bookstores and 624 college bookstores. The company next month will start shipping a competitor to Amazon’s popular tablet reader Kindle, called the Nook.

Burkle, who made his fortune in supermarkets, has been expanding into media properties in recent years and has been considered a potential buyer for the Los Angeles Times.