Book to movie adaptations - The Hobbit

Nothing harder than turning a book into a movie. One type of storytelling turning into another. But such different ways of storytelling.

In a book you can explain, tell what people think, how they feel. In a movie you have to show. You can let the person say it out loud, but it still is different than somebody reading about it.

And when reading people use their own imagination, what they know about live, what they have experienced, how they see the world, to complete the story. A movie shows the vision of the director and screenwriter on the story.

With a beloved book like The Hobbit it is even harder. The book has been around since 1937, millions of people have read it. Know it almost by heart and have their favourite characters. But the movie is showing what Peter Jackson thinks the characters looks like.

I'm going to use The Hobbit - The Desolation of Smaug to explain.

Beorn, "He is a skin-changer. He changes his skin: sometimes he is a huge black bear, sometimes he is a great strong black-haired man with huge arms and a great beard."
From this I have always seen a big, broad man. Not a giant, but a muscular, black haired man. Very large, both tall and wide To use an image, more like Hagrid from Harry Potter, only stronger, more muscles.
And what does Beorn looks like according to Peter Jackson 

It does fit in the movie, although I see more a cat than a bear in him.

Another part is spot on with what I had figured:
"Before his huge doors of stone a river ran out of the heights of the forest"
This is what it looks like in the movie:

But maybe somebody living in a different part of the world and having seen rivers of a very different kind their entire life, will have a completely different vision.

What do you think? Have you ever seen a movie that was spot on with what you had read in the book? Or something that was completely different? Please, do tell.