The same can and should be said about any book that purports to advise people on how to become rich.

I wish people were required to include in the appendix of such a book their net worth as independently assessed by an external audit and tax returns and other filings presented to show that they are wealthy and have actually gained that wealth in the manner described by the book.

Even then caution would still be needed as if markets are efficient (or even slightly efficient) then something that provided market beating returns 3-5 years ago (or however long it has been since they gained their wealth) should be expected to only provide market rates of return currently.