Unless you have read the source material do not watch. Plain as that.
My main complaint is that the movie could have easily contained the story of the source material but chose not to and instead left any audience member who had not been informed in the dust. The film does not let you know what is happening 90% of the time other than "guy is on a quest".
It feels like if they were to take the entirety of the Lord of the Rings Trilogy (extended version) and only include the scenes of Frodo and Sam walking to Mordor. Sure it can be pretty at times but not much happens on the way there (and trust me, even the obstacles Frodo faced were more intriguing). Then after watching 2 hours of walking you're told by all the reviews that in order to really get the story you have to read the source material, it's lazy and boring.
Alternatively, you can imagine watching this movie as going into your English class to see you have a pop quiz where you have to explain the symbolism of a scene in the movie of the book your class has been reading, except that the scene is from a chapter you weren't told to read and the audio of the movie is muted. You vaguely get a sense of what's going on from the actions of characters but you're still just sitting there confused hopelessly looking for meaning that you can't find. Then looking at the reviews after is like seeing everyone's scores on the test posted at the front of the class, some people read the entire book and got A'a but most people didn't and got F's.