Minor screed:

At minumum, 70% of business books are drek. And I'm talking about the bestsellers. I think of them as "self-help for people who have jobs but want careers." On average, the self-help books I've read are 70% drek too. So at least the genre is consistent. Both sub-types share this virtue: they give you a way to feel like you're doing something on your own behalf by investing time and energy in reading them--even if the ultimate 'message' is just an assemblage of familiar platitudes that you'll never act on anyway.