To start with, I thought it was pretty good over all. James Hall (the author) studied 12 bestselling books that were published in the last century and tried to find common aspects that all books had that made them mega sellers. (And he was looking at megasellers, not purely bestsellers, as well as break out books - books written by previously not very well known authors, so that only the book - not the name on its cover - explained why it became a huge seller.)
Some of the aspects I thought weren't very relevant, IMHO. (For instance, he mentions religion as being critical to the book - which I find kind of interesting as religion only played a very minimal role in, say, Gone with the Wind . And sex also was key, according to him, despite that I don't really remember it being all that important in, say, The Hunt for Red October. Plus, these two elements are so prevalent in novels that it would be hard to find one that didn't even have a hint of sex or religion, you know?) But I do think that he made a lot of really solid ones including:
1. To become a mega-bestseller (vs. just a decent seller), you need to appeal to people who don't read books on a regular basis. (Or at least don't buy books.) Even if every single person in the US who normally buys books bought a copy of your book, you wouldn't sell as well as any of these books did. So you need to appeal to a group beyond the regular book buying contingent. This means that your book can't have super fancy, hard to understand language, or elements that would mostly appeal to a serial reader. (For instance, a super unique plot is going to appeal more to someone who's read thousands of books than it would to someone who only reads once in a while. The same is true for vivid imagery, lovely writing, etc. None of these might hurt, but it's not going to make for a mega-seller either.)
2. The characters in these novels are rarely self-reflective. They act. They don't sit around and think and feel and discuss their place in the universe. They go out and do stuff.
3. Most of these novels are movie friendly (and were eventually made into movies). This may not be necessary for a mega seller (as most sold well prior to having movies based on them), but...if you want a bestseller, it may make sense to ask, "Is this the kind of thing that would make for a good movie?" If the answer is no, then you may not have a mega-seller.
4. It hits hot buttons. Virtually every novel covered hit some kind of hot button that was a big deal in the day. (And generally still important now. Valley of the Dolls is really the one exception to the "still relevant now" rule.) Essentially, a novel that doesn't cover any bigger themes isn't all that interesting to most readers. (Even if it covers them crudely, like The Da Vinci Code.)
5. There are almost always intricately described worlds which the viewer may not be familiar with. Whether this is a town, a secret society, or the ante belleum south, readers seem to like learning something new. (Or at least feeling like the author knows what they're talking about.) That world building and research matters!
Looking at books that are too new to be covered (Harry Potter, Twilight, The Hunger Games) I think that most of these actually meet these criteria fairly well. So there may be something to these rules, such as they are. Not that I think that writers should write to them. (As there are a lot of books that ping all these boxes and yet still don't become best sellers. And there are a lot of good books that don't sell all that well and are still desirable.) But I think that it's definitely work a read for someone who is either trying to write popular literature or just wants to know what makes people read.