I read this book when it first came out and thought it was ridiculous. McDonald claimed that the Mexico City mystery man was Saul, the ultimate assassin of JFK.
Saul was firing from the County Records Building while Oswald was firing from the Texas School Book Depository. Oswald's shots missed and Saul's shots hit.
It's hard to believe they reissued his book for the 50th anniversary of the JFK assassination.
The HSCA actually talked to Hugh McDonald:
McDonald was the only person to ever find Saul.
Previous Relevant Blog Posts on Conspiracy Theory
The famed Canadian novelist wrote a good article for Playboy Magazine on conspiracy theorists.
And specifically Oliver Stone.