Everyone that reads my book is surprised to hear it's not topping the charts or plastered everywhere my audience hangs out. My book beat out all the competition when it came out in terms of reviews.
While the points in this post are valid, I don't believe they get to the bottom of what holds back sales.
Frankly, I don't know what the answer is -- I have a vague idea of what it could be but I haven't had a chance to try those things. Perhaps if my book had been in all airport bookstores a few years ago, it might have taken off (no pun intended) like Tim Ferriss' book but who knows.