One can say that a movie has a different impact on every person, and I agree with that, and i do realize that this is not a very well-made documentary per se, but it caused a major impact on me, very much because i wasn't expecting such a tremendous amount of information when i first thought about watching it.
I was, in fact expecting to see some kind of biography and a scratch on the surface on Moore's most popular comic books, and that documentary really have these features, but eventually it becomes a rare piece of modern philosophy and a way to relate with the world that at least for me was entirely fresh and new. A view on the subject of magic that totally made sense to me, and a reflection on our day and age that is realistically terrifying.
Yes, you'll watch a 80-minute monologue by Alan Moore, but I highly recommend it, because if you pay attention, this can be a very enriching experience after all.