For anyone who has already read Naomi Klein's
The Shock Doctrine: The Rise of Disaster Capitalism, the documentary will not come as a surprise but more a shortened, summarised version of it. As such it works reasonably well - it will remind you of the main thrust of the argument, bring up the main examples and show some of the less savoury ones in graphical form - giving them more of a shock power than words alone can.
Where I felt the documentary worked less well is that the book's content - primarily the presentation of the arguments, and then the last part (on a possible shock resistance developing) - needed to be cut down quite a bit in order to fit into the timeframe given. This will not really matter much, if the viewer is already convinced of the merits of Klein's position. If that is not the case, however, it is unlikely to sway someone more sceptical, as it could well be perceived as treating the topic a bit too superficially. While I understand that the documentary format will not be able to completely replicate a book, an added 15 minutes could very well account for this point (and it is not like it drags on as is, so an extra 15 minutes would not make it unbearably long).
In the end, if you liked the book, the documentary will not bring any surprises and it may be a good way of refreshing your memory in a shorter time than re-reading the book. If you want to know, what the argument is really all about, I find you will be much better served by delving into the book first, as the documentary tackles a lot of the arguments in a headline, rather than in-depth manner.