I agree that they did a good job with LotR.
One thing that made their job easier is that Tolkien goes on for pages describing the scene in intricate detail. It's easy to capture that with a 15-30 second camera pan at the start of the scene.
I have the extended editions and I watched the extra material. They talked about the decision making process when writing the screen play. Their #1 rule was "if it's not directly tied to the story of the ring, it's something we can take out." That's why whole sections, like Tom Bombadil, are entirely missing. While it's interesting stuff, it's not directly related to the story of the ring. And with only a few hours per movie, they couldn't fit everything in and they ended up making some changes to fit more of the story in to less screen time.
But that is why so many movies are so different than the books. They just don't have time to fit everything in. So they make changes. Sometimes it works, sometimes it doesn't. With LotR, they put a screenplay together that flowed well and kept the essence of the story going. That doesn't always happen when they go from the book to the movie, unfortunately. But it's great when it does.
I ended up liking the movie adaptation of Ready Player One. The book was great. The movie, I think, told the story reasonably well. It helped that the original author was involved, as was Stephen Spielberg. The book was able to get deep into the nostalgia and really tell a great story. The movie only had 2 hours to tell the same story. While they made some fundamental changes, what they changed it to made sense in the context of the environment. Sections were entirely different, but it worked. The car chase at the beginning was able to communicate a lot more than just the fact that the contest was in process. In just a few lines at the start of the race, you find out just how poor the main character is in a way that flows well. They were able to fit so many other pieces in that way without it seeming like they were just doing scenes to check a box on the plot sequence list. It all flowed well.
The Martian was another good adaptation from book to movie. Mat Damon captured the essence of the character. They cut stuff out to fit in 2 hours but what was left seemed to flow pretty well. I was able to enjoy both the book and the movie in this case as well.