… and have any comments? 
Good book for purpose of showing human potential…
I have read the book. As Kosta has suggested, us readers should accept the validity of the accounts --his testimonies of what John could do. But he said that we could disregard John’s own metaphyical inquiries (i.e. God). The book does a good job showing what we as humans can do through the use of chi. But it does not outline how to practice yourself. A good book for this purpose would be “Qigong Empowerment”. It is amazing though what Chang can actually do.