THey aren't telling the whole story though, they're still only telling facets of the story.
There's no dinner scene, the relationship between Jessica and Duke Leto is cut very short, and Liet-Kynes is killed off way too quick, in a completely different way than in the book. And all of these things are pretty significant to the plot.
I mean I like it, but they're focusing on telling one tiny bit of the story, and they're also kinda making Duncan more of a character than he was in the book.
And what the fuck is up with the whole laserbeam chasing a flyer scene? I'm pretty sure the whole reason, we have shields, and we don't use lasers, is because it causes a small nuclear reaction, so it seems like a really dumb scene to put in there.
I mean it's a cool looking scene, but it's not in the book, and it's canonically false.
Don't get me wrong, I really liked the movie, but it does not do the book justice, not even close, it's like a 8/10 if you just judge it solely as a movie, but if you're judging it as a movie attempting to do Dune justice it's probably 6.5 or 7.