I'm sure we all have favourite book moments which "make" the whole story for us.
I know I have far too many to list here though sometimes, with films, you get something which adds to the original tale.
One great example of this is the song Marley and Marley from The Muppet Christmas Carol. I still think that is the finest adaptation of Charles Dicken's wonderful novella.
But what great films can do is add something special. This can only be done when you've got superb stories to work with in the first place, mind you!
Am sure Dickens would be pleased and it is fabulous to think A Christmas Carol has never been out of print. I don't think it ever will be.