Self-help books are like placebos, they really don't do anything for you but if you read one you'll believe that you can be successful even though most of them are full of platitudes and not much actual content.
But on the other hand I think this is the most important part about them, they give people the feeling that they can succeed which is a necessary ingredient to taking risks to making yourself successful.
Like a rough economic cycle, picking up a new skill, or learning to program, sometimes I have to slog through something difficult that does not seem to be getting me anywhere before the light bulb goes on and I realize "oh, THAT'S why this whatever is done that way."
What's that other adage? Fake it till you make it?
But on the other hand I think this is the most important part about them, they give people the feeling that they can succeed which is a necessary ingredient to taking risks to making yourself successful.