Self-help?! I'm there.
It has good advice - never criticize, show appreciation - and the author reminds us often as to the potential monetary gains from basically caring about people instead of just yourself, but he hasn't yet adressed the gains we can make in ourselves.
It feels GOOD to pay someone a compliment and they brighten up. Sometimes you have to look pretty deep, but most people have some place you can reach them. (Many a relationship has its roots in a shared love of cats!)
When you're nice to people, nice things happen. People sometimes let you go ahead of them in line at the grocery store. Or you get a great gift or other 'pennies from heaven', I call them. Sometimes life just goes well for awhile. It's because when you're nice you can bring out the nice in other people and that makes the world a better place.