It’s not uncommon to find something in Jackson’s films that somehow betters Tolkien’s original, dramatically speaking. Here’s what Brian says about diction in ROTK, film vs. movie:
For what it’s worth, its tone and style is so like the other two movies — whereas the third book is so profoundly different from its predecessors, all stilted and high-tongued — that it’s another testament to Jackson’s abilities that he made it into such a well-rounded unifying piece for the story arc.
I’m re-reading the book now, and it’s all declamation and description, rather than the ordinary dialogue that began the trilogy. (Which, I suspect, reflects how the book was written.)
Think I’m going to need to see it again.