I can recommend
No More Mr. Nice Guy.
If you follow the advice in the book, the people in your life might not like the new non-pleasing you. I would be prepared for resistance from friends and family. Also, from own experience - be careful about how you say NO. If a friend asks you to help him move during the weekend and you don't feel like it because you've had a long week at work.. then say exactly that! Don't make up some lame excuse for why you can't help. Be honest.