I read what I think must be the original one, called "Buffettology." I guess it's worth reading if you've already paid. IMO the text parts are better than the math parts.
IMO the math in that book badly overestimates intrinsic value. It's filled with double-counting. By analogy, she counts both the ground-up cow carcasses that go into the feed, PLUS the value of the new crop of beef. But the former is really a cost of the latter.
I think Hagstrom also tends toward the same error. They both play pretty fast and loose with discount rates too.
You have hit on one of my pet complaints about several investing books. Perhaps one of the reasons that Hagstrom and others can't invest as well as Buffett is that they can't even properly calculate discounted cash flow, which any business school student should have mastered. It is fairly remarkable that reviewers of investment books are reluctant to point this out. I can't believe they all miss this important point.
I think all the book recommendations were good ones. I also like Roger Lowenstein's books on Buffett: The Making of an American Capitalist and When Genius Failed about the Long Term Capital Management fiasco. Lowenstein is gonna be in DC on Feb. 3 at 8 pm at the Smithsonian to discuss his latest book: Origins of the Crash: The Great Bubble and Its Undoing. I'm planning on going to pick up the book and his autograph...if any of the local hogfarmers are also going...let me know ;-)