I bought it in the early 90's when I was in my early 20s after I'd been training several years. He later admitted that he made all that "Bulgarian" nonsense up. He was very good (if dishonest on some things) at marketing, and he obviously figured that saying he stole this top secret training system from the world's greatest weightlifters and adapted it to bodybuilding would give him some credibility, since he was an unknown. He always had the hardcore photos and hype in his ads, and he also claimed to be drug free, which was an obvious lie. He also claimed to have trained Kevin Costner and many other people, which I don't know to be true or not. And I'm pretty sure he took some serious liberties with "expert reviews" and client testimonials. He later brought Platz onboard, which no doubt gave him even more credibility with us meatheads.
I was a drug-free college student and was also working more or less fulltime back then, so there was no way I could do the double and triple splits he recommended for more advanced trainers. And I knew the more novice routine where he advocated one workout a day, doing several bodyparts for just a few sets in each workout would not work for me - I need to work each bodypart with more volume and less frequency for my workouts to be truly productive.
There was one thing I got from the system that made it worth the $50 or so I paid for it. That was his belief that training routines should be modified every 2-4 weeks to keep the body growing. I think that's an important thing for those of us who don't have the great genetics to grow from just about anything. I still modify my training every couple of weeks. The changes are not radical, only subtle - slightly higher or lower reps and loads, slight changes in rest periods here and there, changing the order of exercises a bit, alternating a couple of exercises for a bodypart every other workout, etc.