Breaking Dawn is, while a satisfactory conclusion to the story of Bella and Edward, not particularly necessary to the series overall.
At the end of Eclipse, we were left with a hope for a promising future with Bella and Edward, and while the fact that she hadn’t been bitten yet was troublesome, who truly could doubt that it would happen? With Breaking Dawn, Meyer brings us back to our favorite characters, but it wasn’t such a happy reunion for me.
I admit, that I enjoyed seeing the reaction of Charlie to Bella’s wedding, and there were many revelations that enriched the story as a whole. But writing an entire novel to fit these things in seemed superfluous. Overall, I found much of the book melodramatic and slightly annoying and I believe that these things could have just as easily been incorporated into a short story or two; and would made it a much more enjoyable read.
What Breaking Dawn lacked, compared to the other novels, was real substance and conflict. While I have never read the Twilight books for their intriguing plots (which are quite predictable at times), they still have included major dilemmas for characters I loved. There was also strong motivation for the choices the characters made, and the actions that they did. In this installment, however, all major conflict was resolved nearly within the first half of the book.
Much of the last half of the book is spent describing preparation for a major event that ultimately amounts to nothing.
All in all, I think that this last book was just a piece of fluff that, while it happily ends the series, was not quite necessary.