Getting the facts straight
This is a thorough look at Barnes & Noble, but contains several factual errors that mislead the reader.
1. Categorizing John Malone's $204m Liberty investment as a "rescue of the business" is misleading. As you point out, Barnes & Noble is a multi-billion dollar company: $200 million is more "an expression of interest" than a rescue. Liberty's investment was coincident with the Burkle maneuverings but "this is what necessitated the Liberty rescue move in the first place" is simply incorrect.
2. The statement "a number of companies have fought in the past over ownership and potential breakup of Barnes & Noble" is also incorrect. No one has "fought" to break up the company -- the idea has been floated by several including B&N management. The only company that fought over ownership is the company you then mention, Burkle's Yucaipa. G Asset Management, a minor player with minimal shareholdings, thought a breakup might benefit shareholders, but was in no position to fight for it.
3. Poison pills do not ordinarily expire -- they are not usually designed as a time-limited defense.
4. "B&N was valued at under $1bn, but had revenues which were around $6bn and growing rapidly" -- again incorrect -- B&N's revenues have increased YTY until recently, but certainly not "rapidly".
5. It is of course easy to imagine that because Jana is active with McGraw Hill that it is somehow eyeing B&N's Nook to be "sold with a captive textbook market place, courtesy of McGraw Hill" etc. But you're completely ignoring that B&N's NookStudy platform already has the required access to all McGraw-Hill textbooks in digital form (as well as all other major textbooks). McGraw-Hill is already a partner in the eTextbook company CourseSmart which finds its success by operating as a "United Nations" of eTextbooks. The textbook market is too fractured and too much in flux for a captive Nook to be an intelligent strategy.
I cover all of these topics and many more in my new ebook: "Stripping Covers off the Hunger Games: How 7 Billionaires are Deciding the Future of Book Publishing in America" (available from B&N, Amazon, Kobo, etc.)