At the time of posting this 'comment', there are ten different reviews of this book by Richard MacKenzie. What I find interesting is that all of these ten different reviewers have one thing in common. They have only ever reviewed just the one book - which is this book by Richard MacKenzie. That is very odd. And each reviewer gives the book a maximum 5 stars.
Whenever Richard MacKenzie posts a preview of anything on Amazon, he includes a hyper-link to the page relating to his book.
My point is that I am not convinced about the authenticity and possibly even the existence of most of not all of the ten 'reviewers' of this book. If my suspicions were to be found to be correct, it would not be the first time that the writer of a book was involved in fraudulent self-promotion. Some get caught, most do not. But the potential buyer of any product on Amazon has a right to be sure that all of the reviews are genuine and trustworthy.