Hard To Be A God

Just finished reading Arkadi and Boris Strugatski's 1964 novel Hard To Be A God, in lieu of the 2013 film adaptation which I have yet to see. I'm wondering how faithful the film will be to the book, considering all the trailers I've seen so far (including the opening 17mins currently up on youtube) suggest the film is closer to the fever dream of Marketa Lazarová than the Strugatski's narrative-driven novel, but we shall see. One thing I found quite starting was the unlikely link the book has with Star Trek, more specifically the Star Trek concept of the Prime Directive, a code of non-interference in the affairs of alien civilizations, which is a core philosophical dilemma of the book (the title in fact hinges on it). Incidentally, the first film adaptation of the book was made in 1989, a German-Russian production (which includes an appearance by Werner Herzog), and is available to watch in it's entirety over at youtube (English subs can be activated using the caption button)