I've been a huge fan of the books and a sci-fi nerd for 30 years; this is probably one of the best movie adaptations of any book that I have seen so far, and definitely one of the best scifi movies I have had the privilege to watch. It's no small task, the narrative is notoriously complicated and historically difficult to adapt.
The story as it is told in the book is almost somber by comparison; for the initiated, I think Denis did a fantastic job in terms of direction considering how he managed to "fork" the story line from the original without sacrificing any of the most impactful moments in the book.
For the uninitiated, there is a moment in the novel (portrayed in the Part 1 movie) where Paul is having his first hardcore hallucination in the tent with his mother. He sees the paths he could take, and in the book, decides to take the path with the least amount of collateral damage. In the movie, Denis pulled no punches and did a masterful job of making the story far more palatable for the big screen by leaning hard into the alternative path mentioned by Paul in that part of the novel where Paul says in his internal monologue during the hallucination that "I cannot go that way." He even included the one distinct line of dialogue between Paul and the Baron, which, when I heard it myself as a fan of the book, made everything click in the most satisfying way I could have ever wished for.
In my opinion, this movie was the best possible adaptation anyone could have made while keeping the concept approachable for the uninitiated.
Watch it in IMAX.
Trust me.