This book was recommended to me by a psychologist and it took me about 3 days to read it completely through. And as soon as I finished reading it, I started re-reading it. I'm not sure I'll ever need any other book on assertion and passiveness after reading this one. There's really nothing else that can be said about the issues.
And what are the issues? Well, Salter argues that nearly every psychological problem is caused by a lack of excitation (or assertion). Where did these problems come from? From our parents and society who conditioned us just like Pavlov's dogs when we were young and impressionable. All we really need is a healthy excitation (or even sadism) to be happy in life; and there are numerous ways to condition excitation and practice it.