Six years ago, I read Gary L. Stewart's book The Most Dangerous Animal of All as soon as it hit bookshelves. I remember the publisher had kept it under wraps, as the book offered a promising new theory regarding the identity of the Zodiac Killer. I read it with great interest, but I never saw it as one of the titans of the true crime genre due to its ambiguity. A four-part documentary series based on the book premieres on FX on Friday night (and is available on FX on Hulu the next day), and it boasts some …