The real problem with the book's criticism of the downward sloping demand argument in economics (as presented in the review) is that the example fails to hold wealth effects constant. If you hold wealth effects constant, then the argument from economics is pretty close to unassailable. Seems to be a poor choice of where to criticize economic theory when there are so many other juicy places one could do so. Suggests to me that the author of the book is not a credible critic.