It stated at the website:
"You Can't Lose With Our 100%,
45-Day Money-Back Guarantee

Your total satisfaction is guaranteed. We have a 100% money-back guarantee. We believe you'll find the answers you are seeking. Thousands of other people just like you have been cured using the methods in my book.
I am so confident that you will get everything you need that I promise I will refund your purchase price within the first 45 days if for any reason you simply ask for a refund.

No questions asked.

I take all the risk."

It happened that these are not the answers I want. I emailed them many times requesting refund and even open a dispute and escalate the dispute to a PayPal claim. But paypal replies are:
"Our investigation into the following transaction is complete. As stated in our User Agreement, the claims process only applies to the delivery of goods. It does not apply to complaints about the attributes or quality of goods received. Therefore, we are unable to reverse this transaction or issue a refund.

In the end, I don't get any refund. Despite many emails have been sent but seller ignored all my request. Obviously, this seller actually use the tactics of money back guarantee to gain more sales but will not honour as promised. Therefore consumer must be careful in dealing with this kind of sellers.