Usually I'm not a fan of book-to-movie adaptations, especially deep worldbuilding ones because they're usually done poorly (Looking at you, Great Gatsby) but I'm happy to say that with Denis Villeneuve's Dune, it is certainly faithful to the source, with the exception of a few things that I felt were not drawn out enough or not explained properly.
I was also a bit disappointed with how abruptly it ended, not to say that films can't handle an abrupt ending well as evident with Lord of the Rings: The Fellowship of the Ring, but Dune didn't exactly handle it well unfortunately. However, I have high hopes for the second part when that may release.
Overall, I would say that Dune (2021) is certainly worth a watch. The visual effects are top notch, the story telling is extremely well thought out, and (for the most part) it is faithful to the words of Frank Herbert.