Microsoft already owns a substantial stake in the business, but the technology industry website TechCrunch reported the company was proposing a $1 billion offer to buy the rest of Nook's digital assets. Nook Media also includes the college bookstore chain.
It was not clear from the TechCrunch story whether Microsoft has formally made that offer to Barnes & Noble's board, or whether Barnes & Noble has replied. Barnes & Noble declined to comment and Microsoft was not immediately available.
The Nook business has struggled in the face of heavy competition from Amazon.com and other players in the tablet market. Just this week, the company slashed the price of its top-end Nook tablet by one-third as a special Mother's Day promotion.