I strongly recommend that you read the novelization. There is so much more in the book that makes the action in the movie even more tragic. You get thoughts, emotions, and fears that simply cannot be represented in a movie.
Natalie Portman certainly had a sucky role in this film. She comes across as needy and clingy, and she apparently never gets out of her own apartment. She just sits on her couch and stares out the window. It is impossible to believe this is the same character who ruled as Queen of Naboo at the age of 14. She's still hot, however.
There was one scene in the book that I was looking forward to, but it was not in the movie. It would have been the penultimate scene, with Yoda, having landed on Dagobah, looking around at the desolate swamp where he will have to spent the last decades of his long life.
"When 900 years old YOU reach, look as good, you will not. Hmm?"