I think a book like this, which makes some really big claims, should, roughly, do the following:
1) Present it's premise clearly
2) Since it's a self-help book explain clearly what you need to do
3) Provide compelling evidence that it's ideas work
4) Be credible.
The book does a decent job of explaining its premise, which is that everything in your life is the result of the law of attraction. I quote, "the law of attraction says like attracts like, so when you think a thought, you are also attracting like thoughts to you." In other words, think good thoughts and good things will come to you and if you think bad thoughts then bad things come to you. I've simplified this a bit but not a whole lot as the concept isn't rocket science.
Now, does this book explain clearly what you need to do? Actually, for a self-help book it does a very poor job of this. How do you control your thoughts? What kinds of practices and thinking produce the best results? The author and contributors basically tell you a bunch of stories about how "so and so did something and you can too by changing your thinking".
And that's it for the "how to" part of the book. There isn't any.
Now, if I wanted to prove something worked from a scientific perspective it would seem to be easy to test this stuff out. You take two groups of people, teach one the secret, let the other go on with their lives and see what happens. In theory those that know the Secret would be happier and more successful than the control group. It might not be perfect but it'd be a whole lot better than what we get in this book. But, of course, you'd have to have an actual methodology to test.
Instead the authors cite numerous anecdotes of how the Secret worked. One person's cancer went away. Another individual walks after a brutal accident. Still another finds romance. That's all fine and perhaps it's evidence but it's not proof. Cancer can be misdiagnosed. How many people who were injured like the "Miracle Man" never walked again despite the best attitude and trying the approach perfectly? The problem with anecdotes is that it's easy to start with a result, work backward and assume the conclusion. It's also very easy with anecdotes to only present the ones that make your case and ignore those that don't (when someone dies of cancer while practicing the secret for instance). It's just not good enough to use anecdotes for large claims like those made in this book.
The following quote struck a nerve.
"People hold that for awhile, and they're really a champion at it. They say, `I'm fired up, I saw this program and I'm going to change my life.' And yet the results aren't showing. Beneath the surface it's just about ready to break through but the person will look just at the surface results and say, `This stuff doesn't work.' And you know what? The universe says, "your wish is my command,"
I thought it was interesting that the universe instantly manifest failure but isn't quite so fast with success. In fact, a cynical individual might conclude that what they are really saying is, "when this program works it's because the secret always works, but, on the off chance it doesn't work, well, that's your fault." An even more cynical person might think, "gosh, I wonder what would help a person who failed? Maybe, a seminar with Bob Proctor would be just the thing to get them over the top?"
Lastly, is the Secret credible? On the one hand, I think a lot can be said for the idea that if you change your thinking you'd change your life. In many ways that seems obvious to me.
On the other hand, if the secret actually was true, especially at the scope claimed by the book it would mean that everything that's happened is the result of your thinking. So, when a child dies of pneumonia, well, it's because they brought pneumonia into their lives. Michael J. Fox, not only did you bring Parkinson's into your life but change your thinking and it will go away. Obviously these things aren't true and they obliterate, in my opinion, any credibility in the book.
Not only does the book go too far but most (I'd argue nearly all) of the contributors aren't credible. On a topic of this scope: the ability to 100% change your life and the world in an incredible fashion, does anyone really think you couldn't find psychologists, top flight scientists, therapists and thousands of mainstream individuals to support it, if it worked? Wouldn't there be tons of research instead of anecdotes? Instead we get a Feng Shui Master, a chiropractor, motivational speakers (err trainers), a metaphysicist, etc. combined with a half dozen anecdotal stories. So the most powerful like changing idea ever and you get it from the crew in this book presented in this fashion? I don't think so!
If this idea really worked, at anything other than giving material to self-help speakers and generating repeat students, it just wouldn't be found here. The book wouldn't even have to be written because we'd all already know it and be practicing it. Remember, this is not a new idea, it's been around for a very long time, and it's been the topic of literally thousands of seminars and hundreds of books.
In conclusion, I'm not opposed to the idea on a small scale but this book just goes way too far and I'm left with the feeling that all that's really going on is a bunch of people trying to get their name out and get you to pay for their seminars.