I think books like this sell because the subject matter is easy to understand, but brings about some sense of superiority in the reader for knowing contradicting theories. These books succeed due to the shock value of the information they contain. This is in a similar vein to the Penn and Teller show "Bullshit". If you say something loud enough, and sound relatively intelligent in the process, people feel smarter when they hear it. I feel that the same is true about Malcolm Gladwell's writings.
The only problem is that the shock value of the content is in no way related to how valid the information is. "Bullshit" is terribly biased towards the presenters opinions, whereas books like these are biased towards whatever makes headlines, which results in varied levels of validity.
The only problem is that the shock value of the content is in no way related to how valid the information is. "Bullshit" is terribly biased towards the presenters opinions, whereas books like these are biased towards whatever makes headlines, which results in varied levels of validity.