The great thing about this book is it is not about how to sell or achieve wealth or become successful, but how to live your life ethically and with kindness. When you disagree with someone, Carnegie advises you to say, "Well I may be wrong." And you very well may be! When a clerk is nasty to you, Carnegie advises empathy instead of anger.
I've read this book about eight times and I've given copies to my children and my friends. It's time to for me to read it again.