Well, now I have seen the film adaptation by director Paul Thomas Anderson of Thomas Pynchon's novel Inherent Vice.
The film follows the story of the book rather faithfully, but cuts a lot of it. This is of course inevitable in any film adaptation, but in this case it becomes somewhat of a problem. The cuts make the film very incoherent. The book was already rather incoherent, but the film is far worse in that regard.
I have read the novel and still found the film very hard to follow, far more so than the book. One can only imagine how confusing the film must be for someone who hasn't read the book.
Sadly, the thematic concerns seem to be somewhat lost in that general incoherence, Pynchon's argument weakened due to all the cuts.
The problem really is that Anderson's direction doesn't shed any new light on the story, or do anything really creative with it, he just re-tells it. And so with all the cuts, you lose a lot in the translation to film, yet don't really gain anything. There's really nothing here that wasn't done better in the book.
It's sad, for the film is well-made otherwise. The very look of the film is wonderful. It is shoot on grainy and colour-saturated filmstock, so that it looks like it was made in the 70s. The acting is truly excellent throughout the entire film. Even minor roles are strongly cast. This makes many of the individual scenes and jokes come off successfully.
So despite the film being a bit of a mess as a whole, it is often an entertaining mess. If you see it without any expectations to understand the plot whatsoever and just go with the flow, it will be a fun but confusing experience. I do however miss the substance of the book and all the wonderful material that was cut from it.