Any time you derive so much enjoyment from an author's output, you owe that author your gratitude. So, thank you, S.M.
That said--the (possible--it leaves plenty of room for a sequel) conclusion of the Twilight train wreck is, in a word, UNACCEPTABLE.
I don't want to give anything away, and frankly, I'm thoroughly sick of this book, having slogged through it for weeks and only to punish myself for paying expedited shipping fees to my current residence in the Netherlands when I was in the throes of my Twilight fascination. While I deliberately prolonged my reading of the other (progressively lackluster) Twilight books, so as to luxuriate in the delicious purple prosiness of it all, I prolonged my reading of this one because it was a chore to finish.
Suffice it to say that the bloom doesn't fall off this rose--it leaps. There are glimmers of what made Books the First through the Third such cringe-inducing guilty pleasures; this only makes one long for the Halcyon (I can't pronounce that word, but I can spell it!) days of (the more sloppily written, and infinitely more enjoyable) Book the First.
A few things I can say without spoiling anything:
Suspending the inclination to assign any fixed qualities to any of the characters you've followed through Books 1-3 will make this book much easier to get through. One thing that does remain somewhat consistent is that, for someone who's supposed to be "self-effacing," Bella is awfully aware of every nuance of everyone's perception of her at all times.
Speaking of characters, about thirty or so irrelevant and completely peripheral ones will be introduced very late in the game. Unless there is a sequel (dear God, please no) coming, this is a complete waste of space.
Be prepared for the book's descent into a heavy-handed Anne Riceian attempt at a Novel of Ideas.
If you're an obsessive sicko like me and you've come this far, of course you have to finish Book the Fourth. All I can say is that I don't envy you.