By someone who has not seen the film, I was warned "it won't be as good as the book. They never are."
In the case of 1984, the two are not mutually exclusive. Had I not read the book, the movie would not have made sense. It seems as though this cooperation of media was intended. There are innumerable subtleties which are explained in the book, but are left unsaid in the movie. The movie does not explain what happens - that's why you read the book. The movie shows the contents of the book. On the whole, the film was very true to the book, with minor differences (the passing of Goldstein's book, for instance). The film was not entertainment: it was demonstration, it was expression of Orwell's thoughts. The things which make you wince as you read them make you wince as you watch, the parts which force you to think make you think again. Knowing the outcome is irrelevant. And, for that, I recommend the movie to anyone who has read the book, especially if it was forced upon you in the name of education.
Everyone else should read the book anyways.
And, the soundtrack full of prototechno music from the Eurhytmics was excellent.