I disliked the book intensely for the simple fact that, while being a fine book on it's own, as part of the series, it made absolutely no sense. Here's why-
1. After three books of being a normal high school girl, Bella is suddenly whiplashed into being married and immortal with child. There is no grace adjustment- she is just snapped off of being everything she was and totally transformed into something unrelatable in the LAST book.
2. All male vampires have apparently become Incubi without their knowledge in the eleventh hour. Any male vampire anywhere within the Twilight world has always had the ability to impregnate a human girl. We do not know how many cases there have been, how many mutant children are running around, if it is possible to have just a BIT of vampire in you provided it is bred out, or how it is even possible, when venom burns through everything and would have logically erased any live sperm in the transformation process. People, it dissolves contacts and petrifies skin tissue.
3. The La Push pack are evidently NOT werewolves, but shape-shifters, though we have spent two books calling them werewolves. This information is thrown in casually, without need, and without any further information. We weren't even thoroughly explained to about what a real Child of the Moon is, or shown. Besides the requirement of a full moon, how are they different?
4. The Volturi showdown which has been built up since New Moon, is resolved by them marching into Forks, gliding around a bit, and running away with their tails between their legs. No, it was not a "mental" battle- it was not a battle at all. The Volturi decided they didn't want to risk anything and turned around.
5. The love triangle which spurned thousands of dollars in Team Edward/Jacob t-shirt sales never existed.
6. Stephenie Meyer kept to her original plotline of Forever Dawn, even though it no longer fit. When asked to write an additional two books of Bella's school years, every plotline shifted and grew and became ready for an ending which was exceedingly obvious to everyone who had read the series. But indeed, she plowed on with it anyways.
7. Bella's transformation became an only option, rather than the price, the choice, it had been since book one.
8. Human Bella and vampire Edward having sex, though physically impossible, is forced on us multiple times, as an illogical plot device to lead to Renesmee. Edward has always put himself in charge of Bella's safety, and yet is putting himself at great risk of killing her, if only to grant her a little pleasure in the bedroom. Bella's argument was that she wanted to experience intimacy before she became blood-crazed, though Edward should have known from the thoughts of his family that vampires still experience those feelings, even in greater desire, and reassured her that she didn't need to risk her human life for something she wasn't going to have to give up.
9. Bella should not have been such a docile, rational newborn. Yes, it is very possible that she be better than average (granted all her mental preparation), but not to the Carlisle-degree that she was. Newborns are said to be WILD even after months of understanding what they are and what they're doing. She was just normal temperamental Bella with superstrength. This was a girl who was punching werewolves and throwing money bags through windows as a HUMAN, and who only growls a bit and inwardly complains of throat ache as a NEWBORN.
10. We're flooded with new unimportant characters to memorize, added only as a coolness factor of generic x-men powers (which never get used in any kind of battle anyway, so what was the point? Bella's power alone could have held off the Volturi long enough for them to explain Renesmee, if it was only her power that scared them off anyway.) And if the Cullen's knew sooo many talented vampires, why did they not call them for help in the Eclipse newborn war?