It's just an OK documentary. I'd say very much like some random episode you get your eyes on after some zapping and then you end up watching out of curiosity.
The first installment is by far the least enjoyable. I hated the the tone used on it, an impression rarely lowered throughout. Right afterwards, we get in my opinion the best of this whole doc: the direction and writing for "Pure Corruption" is really good; nice imagery and text. "Purity is a good mask for corruption, [...] it discourages inquiry". Also, the cinematography is great. The final two aren't very good, which makes this doc quite forgettable.
A great adaption of the book.