I actually liked the other Twilight books even though I always felt I shouldn't. They're fast, fun, cheesy reads. Stephenie Meyer did those well.
This, her foray into the darker side of vampires - not so good. Exploring how the non-vegetarian / non-Cullens live... eh. I can see why it would be fun for her to explore that. I can even why it would be fun for her to share with fans. But personally, I'm just glad I read the free online version instead of paying for it as it pretty much just reads like a fan-fic of an obscure Twilight character.
The conversations are awkward. The killings are awkward. How she uses vampire senses - awkward and convenient even as it's being explained, I just don't buy it. It's just so rushed and requires you not to question anything which is rather ironic given the story itself.
The one character that is at all believable as a vampire is the one who doesn't really talk, if that tells you anything about how this is written.
Were people to read this book without the Cullen scene in it and without Stephenie Meyer's name attached, it would flop if it'd even be published.