What makes a bestseller?

Well, beside the obvious -whatever book sells the most copies in a given week/month etc. It seems there is a more fundamental theme than this. Over the last two weekend's I've read two books that are currently bestsellers. Blink: The Power of Thinking without Thinking, and Freakonomics: A Rogue Economist Explores the Hidden Side of Everything. Another one I hope to read soon is The World is Flat: A Brief History of the Twenty-first Century. I have also been exploring the fiction bestseller list. I am currently making my way through Nick Hornby's A Long Way Down, and earlier this summer heard Ian McEwan's Saturday and read Elizabeth Kostova's The Historian. The fiction books seem less related, they appeal more to people's like and dislikes and the development of characters than the commonalities of idea development in most non-fiction books. Back to the point, non-fiction bestsellers tend to aspire to be marketed as academic books. That is that they play on the consumers ego -"Your smart you can understand relatively complex ideas that just need to be taken out of obscure jargon that academics use to scare people off, buy this book." You've got to give the authors some credit for making things seem easy to understand and cutting through the bullshit,and even putting the ideas in the context of stories. The downside being that if you are even slightly a critical reader you are left wanting more, for the ideas to be taken further and some of the research explained so you can learn something about method. That leads to the fundamental principle of bestsellers the authors let the reader take the ideas where they want to go. Get a catchy title, a general thesis, an idea that has some legs and just let the reader do most of the work seeing the implications of them. For example, Blink uses the idea that we have both a part of the brain that works quickly and a part that takes some time- it's basically elementary biology, our hearts beat with out thinking, our fingers, on the other hand (pun intended), take purposeful action by our thinking. If we can just train our brains to be more like hearts then eventually we won't have to think at all. Of course, the Malcolm Gladwell never says this, but take the idea were you want and everyone will pretty much say its a good book (I'm willing to say its have decent, but the ideas aren't robust enough to actually make this a book, its more like a magazine article). Freakonomics is in my opinion a better book, although near the end the authors run out of steam, and end it rather than keeping the train of thought and making this a valuable book. The authors work under the assumption, which is in line with popular thought -which explains why it sells, that life is pretty fragmented and its really up to each person to fit some of the parts together for themselves, you can just imagine the incoherence of this. As soon as you discuss the book with someone else all hell will break loose, well maybe not, but you'll be a little pissed that no one else sees it your way. We read the idea books over the weekend and then mostly forget about them when we hit work on Monday, or maybe there is a more subtle influence. A possible good of these types of books is that maybe we'll actually have a discussion with others that is actually about things we hold to be true, but we tend to ignore this kind of discourse, and stick to the basic common denominator, which if I've succeeded in this post to do, then I may have an idea for a bestseller. Wait...a bestseller about bestsellers? How could I go wrong?