Since Rita Hayworth is so short, it was easy to read in one night. It was a great, quick read. However, I think that my attachment to the film is too strong to choose the film over the book. The images and voices were so strong in my mind that I couldn't stop picturing the actors as I read. Even though Red is an Irishman in the novella, I kept picturing Morgan Freeman. Not only that, but the film delved deeper into the storyline. I found the resolution regarding Warden Norton far more satisfying in the film than in the novella. I kept waiting for Red to say, "how often do you look at a man's shoes," but it never came.
Overall, if you're a fan of the film this is certainly worth a read. It will cost you a few hours, tops, and it will give you an appreciation for what a great filmmaker can do with just a bit of good, solid source material.
Food for Thought... Can you think of any other films that were better than the book that they were based on? The only other film that comes to mind for me is The Devil Wears Prada.