If the information in the book is an accurate reflection—based on what we consensusly know today—no doubt this man was on serious doses, particularly for his era.
Of course, it's just a book, likely with some kind of "disclaimer" about medical advice and so forth... basically considered fiction, right? We take away from it what we want, it's not a non-fiction history or recipe book.
I'm going to put on my "harm-reduction" hat and say: whomever, casual builder to pro, could use books like these—and all the other data currently available—to formulate their own "recipe" for what works to successfully achieve their own goals. Some "recipes" work well, others not so much. Maybe Chase Irons is using the best recipe he can and that's all he'll ever achieve. Maybe he's using the wrong recipe. This method of reasoning can be applied to anyone.
In the end, everones' DNA reacts differently. Each of us has to find and "experiment" to find the winning recipe for our own unique DNA. It's a long and detailed process. This can be said about anything really though, right? However, this is a very complex arena... training, nutrition, recovery, anabolics... many, many critical details.
This man, Markus, obviously found the right recipe for his DNA. Doesn't mean that recipe will work for anyone else. Regardless of what others do or recommend, it's up to each individual to know and discover their own "recipe."
p.s.: I would really like to get a copy of that book in English!