I think this was the least impressive of the Twilight novels as far as I was concerned, and not just because of its subject matter, although that was definitely part of it for this Team Edward girl. Unfortunately, it also had the sloppiest edit of the three, with some spelling mistakes and quite a bit of repetition, although I don't think I noticed either of them until after the fifth time through.
Certainly the story is difficult to read. It's not fun to spend such a long book in the head of someone who's so depressed for the majority of it. However, I'm not one of those who thinks that Bella's state is unreasonable or shows that she is dominated by Edward. That line of thought doesn't ring true, especially since it's clear that he suffers the same way she did. I think it is simply an attempt to try and demonstrate the otherworldly nature of the love of the two protagonists. I'm sure many will disagree with that, but that's the way I view it.
So while this book was a difficult read for the majority of it, the final few chapters did help restore my faith.