It may be called "The Secret," but with nearly 4 million copies in print, the country's No. 1 advice book isn't much of a mystery anymore. The DVD version is also wildly popular, with more than 2 million copies sold so far.
The "Secret's" premise is simple. Love, money, health -- you can have them all, simply by thinking it.
"Thoughts are sending out that magnetic signal that is drawing the parallel back to you," says Joe Vitale, a metaphysician and contributor to "The Secret." "See yourself living in abundance and you will attract it. It always works. It works every time with every person."
"The Secret" is the brainchild of Rhonda Byrne, an Australian television producer who says she stumbled upon it while going through rough times.
To help uncover "The Secret," Byrne enlisted two dozen writers and teachers of diverse backgrounds, including a visionary, a feng shui expert, and a physicist. The book's founding principle is based on what is called the "law of attraction," which they claim is scientifically proved.
"The law of attraction is really obedient," says Lisa Nicholls, one of the contributors. "When you think of things that you want, and you focus on them with all your attention, the law of attraction will give you what you want, every time."
"And this is really fun," says Joe Vitale. "This is like having the universe as your catalog and you flip through it and you go, 'Well, I'd like to have this experience, and I'd like to have that product and I'd like to have a person like that.' It is you just placing your order with the universe. It is really just that easy."
The age-old philosophy of ask and you shall receive has readers flocking to "The Secret." It was even featured for a precious two hours on Oprah Winfrey's program in early February, gaining the endorsement of the powerful host herself.
When Oprah speaks, readers buy, and "The Secret" publisher Simon and Schuster tells "Nightline" the book's sales spiked after Oprah's endorsement, compelling the publisher to request 2 million more volumes, the largest reorder in the company's history.
But with growing popularity comes increased criticism and, in this case, there is a great deal of it. Critics say "The Secret" is not only wrong, it is dangerous, leading people to believe you can get what you want, whether it's getting rich, curing disease, losing weight simply by thinking positively about it. .
I find it amusing that anybody would criticize it," says Bob Proctor, who "The Secret" identifies as a philosopher. "Do you know, it's always been around? The law of attraction is always working. That's like saying the sun's not shining. The sun's always shining. You may not see it, but it's always shining. The law of attraction is always working."
Critics, however, are quick to share their doubts. In the DVD version of "The Secret," for example, a woman claims she healed herself of breast cancer simply by seeing herself as healthy.
"I believed in my heart that I was healed. I saw myself as if cancer was never in my body. One of the things I did to heal myself was to watch really funny movies," she said in the video. "From the time I was diagnosed to the time I was healed, totally, was approximately three months. And that is without radiation and chemotherapy."
ABC News consulted a range of professionals about the claims in the book. Dr. Richard Wender, president of the American Cancer Society, has concerns with the implication that we can create disease or heal ourselves simply by our way of thinking. "I want to be very clear that there is no evidence that people attract cancer by their thoughts," said Wender. "Not only that, I know patients who went through their treatments anxious as can be, convinced the whole time that they would never make it, who today are completely cured because they got good treatment in a timely way."
Wender also worries that people following the guidelines in "The Secret" may reject helpful therapies in favor of positive thinking.
"If some person chose to strictly follow the steps in this book, there is a risk that they could die needlessly," said Wender. "If you have a disease where we have treatment that we know can cure you, and you opt not for that treatment, you will die."
Even Proctor thinks "The Secret" might have gone a bit far on this particular point. "We hear people say, 'Well, we just have to think and then we can get rid of cancer. I don't know anybody that says that. I certainly don't say that. I think if there's something wrong with the body you go to somebody that understands the body and take treatment for it."
Other contentious views include the idea that our lives are entirely a product of our thoughts. Specifically mentioned: If you think you're thin, no food can make you fat. Another claims that if you ask that checks come in the mail instead of bills, eventually you will get them.
"Well, who can argue that thinking positive thoughts and setting big goals is better than thinking negative thoughts and having small goals," said Pete Peterson, a former secretary of commerce. "But to think that wishing makes it so -- I call it a dangerous childhood fantasy."
"Success in business is not about wishing, it's about earning it the old-fashioned way," said Peterson. "Too much planning of your life is a dangerous idea, because so much of success is determined by random, what I call dumb luck events."
Valerie Reiss, the spirituality editor of the Web site Beliefnet, says "The Secret" has been spilled for a while. "It's something that I'd heard a lot before … the idea that we create our own reality."
But that isn't her only criticism. "I mean, the idea we can sort of become our own God, in a way, and tap into this energy force, is very arrogant." Reiss also believes that the book's appeal is due to its clever marketing. "I mean, [it's] genius … [to] call it a secret. Everybody wants to know a secret."
For yet another perspective from Brian Green, a noted physicist at Columbia University, also offered his professional opinion. "If by law of attraction, they have this notion of having a thought and it attracts like thoughts, I can assure you that quantum mechanics has nothing to say about that."
On its back cover, "The Secret" boasts that great thinkers like Plato, Galileo, Edison and Einstein all knew a secret that the rest of us didn't know. Green doesn't buy it. "Look, I've never met any of those guys," he said, "but I have zero evidence that any of them would've held on to any fundamental secret about the world and not shared it."
The final skeptic of "The Secret" was Dr. Louis Aronne, one of the nation's foremost authorities on weight loss. He sees a silver lining, but he still has his doubts. "All in all, I think that there are some aspects of this that can be helpful," said Aronne. "It's very important to think positively if you want to achieve anything."
"I think that's one aspect of this that could be very helpful. But one of the problems we've had in the area of weight control is the idea of magical thinking. And this is almost the perfect example of magical thinking."
"The Secret" has been successful in blending science and faith in a way that readers and viewers can easily follow, and, despite the doubts expressed by many critics, it's no secret that many Americans are eager to learn more. ABC News' Eric Johnson contributed to this report.