There's a misconception about self help books that they teach you "tricks" that you can instantly use to become a completely different person. A lot of the good ones teach you principles that you need to practice constantly to improve. There's hard work and risk taking involved which many people that buy the books are not prepared to do.

The first self help book that actually helped me was How to make friends and influence people. It was hard for me to overcome my shyness and look people in the eye and smile, but with constant practice I got better at it. Taking an interest in people or being agreeable these are all basic principles that genuinely good communicators use, the book just points you in the right direction you have to apply the hard work and courage.

Good self-help books are rare but they do exist.