The research conducted by Dr. Thomas is poor at best. Admittedly this was written some time ago, but still very large and basic facts are incorrect which really dont have any excuse.
From times, dates, mechanical data on the bf110, the markings of Hess's aircraft, all being inncorrect, the list goes on.
Not to mention the fact that the whole premise is based on what seems to be Dr. Thomas "seeing" Hess get undressed for about 10 seconds. How the man can make a proper medical examination from this i fail to see.
The whole book is based on the fact that Thomas did not see any obvious scarring on Hess's chest from where he was shot in the first world war.
It is worth reading for anyone with an interest in the subject, simply as background to, and the origin of the Hess double theory, but it is far from a book that can be taken seriously on its own merit.