This book able to contribute to making peoples' lives a lot more carefree and comfortable. I have no doubt that if each of the agreements are worked on even a little, people would start to see how they're causing a lot of their own grief. It has to do with giving an overhaul to very old beliefs about self esteem, needs and expectations, finally.
I started reading the Four Agreements back in the '90s, but a lot of things got in my way, like mostly my life! I finally got back to reading this book this past year (2011), and have actually been adapting some of it! I have chosen the agreement "never take anything personally" to focus on for now.
I've had a lot of practice with this agreement at work. I've had difficulty relating to some of my co-workers that happen to come from the far side of "woken up", if you know what I mean. They seem to get instantly vicious if they think they are being threatened even a little bit, and sometimes they don't even seem to realize why they feel threatened because their hackles go up too fast. Then in the frenzy, they're oblivious to the idea that maybe they've simply jumped to conclusions before they got all the facts, which is most often what has happened. They are always evaluating how the Universe is impacting them, not how they are impacting the Universe.
The agreements address this type of thing thoroughly, and help the readers see how they have set themselves up, then teaches them how to stop doing that. Unfortunately, there is no good way to expose people to the book when they are clinging to their old beliefs that everything is Happening To Them. It's like Catch-22: they are continually stressed because they're reacting in ways that are based on old beliefs, but their old beliefs will keep them from even trying to investigate the book.