Very different from the movie in narrative, story, and just generally a lot of the weird shit. The movie was much more focused on the visually weird shit as it could be, basically discarding the book's more nuanced weird things. I think both the book and the movie have the same effect though, making you feel extremely uncomfortable, yet curious due to the beautiful nature of the strangeness afoot in "area x".
I definitely got that feeling at the end of the book where I wanted so much more yet was also strangely satisfied by how weird, open ended, and disturbing the conclusion of the book was. Also a lot of the creepy stuff was very well thought out and well described in that it made me feel that sense of mystery and chaotic discoveries one after another that you want from a good creepy sci-fi story.
The characters were different because they didn't have names but were essentially the same in personality from the film. But I especially liked the psychologist's role in the book as a sort of antagonist that made more sense than all the danger around her. The whole deal with the hypnosis made it really interesting to see things through the protagonist's eyes as the conspiracy and lies unraveled around her with her immunity to the hypnosis, allowing all the detail in these fictional accounts.
I was flabbergasted at the description of that "crawler" though. What the hell. How would you even visualize something like that? It's one of those situations where the main threat is just more of a frightening concept than anything, which is really effective here.
However the writing isn't perfect in this book, I noticed myself picking apart the author's style a few times, but I can't remember any specific grievances. I just feel like some elements of the story didn't make enough sense. But that didn't detract from the experience much.
But just what the hell was that moaning creature in the reeds?! Hope we find more out about that in later books.