This is another instance where I saw the movie before reading the book; something I don't usually like to do. However, in this case I was pleasantly surprised to see how closely the movie stayed true to the book. There is a difference in emphasis between the two, though: the movie seemed to focus a little more on the supernatural nature of prisoner John Coffey, while the book was really about guard Paul Edgecombe. Of course, it would not have been a very exciting movie if it had followed much of the minutiae of Paul's life, including his relationship with his wife. In the book, however, it is those little details that bring Edgecombe's character to life. Even though really strange things happen around him, his responses seem very natural, very human, and so do his relationships with his fellow employees in the prison.
I won't go into too much detail, as I think it is interesting to see everything slowly unfold, especially the unexpected twists that take place in and around the prison. From what I can recall from the Stephen King books I have read in the past, this is one of the best-written of the bunch, even though it not as bizarre as some of his others. But that is not necessarily a bad thing.