Activist investor Tom Sandell, a well-known hedge fund manager, is seeking to have Barnes & Noble Inc. (BKS) , the nation's sole "brick and mortar" book retailer, hire an investment bank and sell itself. 

Sandell and his fund, Sandell Asset Management LLC, have frequently sought to install director candidates at targeted companies to drive an M&A agenda. The insurgent fund, which launched its campaign on Tuesday, likely has until mid-August to nominate dissident directors. 

Also, Sandell doesn't usually launch an M&A driven activist campaign without first considering whether there would be companies interested in buying the business, which has a $590 million market capitalization. At Barnes & Noble, there is a hodgepodge of conventional and unconventional buyers that could seek to purchase its 633 U.S. stores.

Barnes & Noble fits within a broader category of companies that activists acknowledge are in industries experiencing a secular decline, though they believe the market is overreacting to that decline so they would work better as private businesses. 

The most likely buyer could be the retailer's chairman, Leonard Riggio, who considered forming an investment group in 2013 to buy the business. Sandell noted that Riggio could take the company private in a leveraged acquisition "at a fair price for public shareholders." Sandell pointed to the Riggio's sale of his college book business to BKS for more than $500 million, to suggest that Riggio has the resources for such a leveraged buyout.

Also, some private equity firms could make a play. Sandell estimates that a private equity firm could pay more than $12 a share, 50% higher than its recent stock price of $8.02 a share. Buyout shop Sycamore Partners LLC's proposed acquisition of Staples shows that deals to acquire retail operators are alive and well. 

However, there are also some less conventional buyers that could be interested as well. One possibility is that a private equity investor could team up with a major publisher to acquire Barnes & Noble if the company agreed to put itself up for sale, with the goal of ensuring that BKS doesn't go bankrupt and that there continued to be a national bookseller rival to Amazon.com AMZN. (Amazon itself is an unlikely buyer because any purchase would represent the kind of book industry consolidation antitrust regulators are likely to reject). 

Industry analysts argue that the biggest publishers have supported Barnes & Noble in the past, suggesting that a combined effort between a PE shop and publisher could happen.

David Schick, a senior analyst at Consumer Edge Research, suggested that there were some book industry dynamics that could benefit Barnes & Noble.

"The publishing community has been supportive of Barnes & Noble in the past, whether it was during the financial crisis or the birth of ebooks and e-readers," Schick said. "Clearly the book publishers want a robust physical bookstore environment and Barnes & Noble is the largest player."

Potential publishers that could team up with a private equity firm include Bertelsmann's Penguin Random House, News Corp.'s (NWSA)   Harper Collins, CBS Corp.'s  (CBS)  Simon & Schuster, Lagardere's Hachette and Holtzbrinck Publishers LLC's Macmillan. 

Also, the recent unexpected acquisition of Whole Foods Market (WFM)  by Amazon, a transformative industry deal, has raised the prospects that there might be other types of non-traditional technology-brick-and-mortar tie ups in the future. People familiar with the situation suggest that the activists believe that there could be some unconventional buyers lurking, such as Alphabet's Google (GOOGL)  or Facebook.

Google, for example, has opened a branded retail shop in London, to display and sell various gadgets, including its voice-activated Google Home unit, headsets, Android phones and Chromecast TV media streaming devices. Google's various devices could replace the section in Barnes & Noble stores currently devoted to selling CDs and DVDs.

Alternatively, in March CNBC reported that Facebook was advertising for a retail manager, with the goal of creating an improved experience for its retail partners, which sells the Facebook Oculus Rift virtual reality headset. Facebook could easily acquire Barnes & Noble, and a deal would provide a venue for its products at the same time that it gives the bookstore chain a social media behemoth to help promote book signings.

One analyst suggested that an unconventional buyer, such as Google or Facebook, could be a possibility in a post Amazon-Whole Foods world. However, Michael Pachter, an analyst at Wedbush Securities Inc., argued that neither Google nor Facebook would be interested. "Nobody needs bookstores," he said. "Facebook does not need a retail presence, and Google does not need a retail presence."

He said that Google may be interested in a few flagship stores, but that they wouldn't want to own more than 600 retail locations suddenly. "There is a zero probability that any tech company buys this," he said.

Also, Quartz reported in 2013 that Wal-Mart (WMT) studied buying Barnes & Noble in 2010. The report noted that Barnes & Noble could help Wal-Mart improve its online sales.

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