Another GREAT book to own if your wanting to get into natural horsemanship is True Horsemanship Through Feel you can buy it really cheap on ebay on at amazon heres a link to the book on amazon
http://www.amazon.com/s/ref=nb_ss_b?url=search-alias%3Dstripbooks&field-keywords=the+art+of+natural+horsemanshipI myself have just recently gotten into natural horsemanship and i promise you once you start you will never look back and you will be amazed with the results you get out of your horses. Another suggestion, I know im full of em hahah, is to look into seminars in your area or clinics. Clinics that you bring your horse to are the best way to get a full understanding of natural horsemanship because you get to see exactly how its done and the results you can acheive in a small amount of time.
Another good way to get an understanding of it is to go to you tube and look up videos on it. You will get to see some on the training methods and clinics for free. Im all about free so thats what i did and it really helped me. I have an abused horse that I took under my wing and have been using natural horsemanship with him and the results I have received are amazing. You never would have guessed the horse has been abused.