> It's so tedious, repetitive, and obvious that I genuinely can't understand what people see in it.
I think that can be said for a lot of books that are popular. It's a bit like applied math vs. pure math. In pure math, applied math is often seen as a "natural consequence". And yet, applied math is what most people view as useful and moreover, pure mathematicians often don't know how to apply mathematics to engineering or physics. Personally, I agree with you, but I think that what is obvious is not always precise, and what is precise is sometimes not used.
I have a sort of moral objection to these kind of books too, but somehow you can both see these books as a sort of moral "cheating" and you can see these books as a useful way to better you relationships with other people (and both viewpoints have merit). I didn't read How to Win Friends and Influence People, but my comment is based on my experience with trying to read *What they don't teach you at Harvard Business School." [1]
[1] By Mark H. McCormack.