What is the difference between the book and the movie the exorcist?

The re-edited version(The Excorsist,The Version You've Never Seen) is much truer to the book than the version first presented,which the director refused to edit further over the objections of the studio. It hews closer to the book, but the film is more time-compressed whereas the invasion of the demon and the actual possesion lasts over months in the book. And yes,Father Karras dies at the end of both