The movie over all remained a lot more faithful to the book than I thought it would. It didn't leave anything out (but sometimes they changed the way it happened a little), and they did add a little. It is very correct that there is no way the movie could compare to the cinema of our minds, and narnia was a book written purely with imagination in mind. I was reading a few of the negative reviews of the books on amazon one day, just for fun, and most people complained that the books were too simple and not nearly detailed enough. The way Lewis wrote them they are simple stories giving you only the most important details and your imagination is suppose to fill in the rest, unlike Tolkien who paints you a verbal painting of what a scene is suppose to be. I think in the 50 + years since the books were written we have become more and more robbed our the ability to use our imaginations.
For the ones who have read the book, it is natural for the movie not to match up to the one that was filmed in your mind when you read it.
I have enjoyed the books since I was very young, and I also enjoyed the movie for what it was, a movie. And a movie can never take the place of a book.