This is pretty standard Twilight fare. I liked it, don't get me wrong, but it was along the same lines as the main series. There were some interesting things about it, like getting to see how Victoria went about actually planning her revenge on Edward and Bella. And seeing things through the eyes of a non "vegetarian" vampire was cool too. I feel, however, like this was a bit of a missed opportunity.
It's a very short book as intended, but it could have easily been made longer. We start out in the middle of Bree's "short second life," and I think I would have preferred that we started out at her vampiric conception. Meyer describes in the main series how many of the characters became vampires, but I think it would have been worth it to actually feel it happening in a stream-of-conciousness style as it was happening instead of being told in retrospect. Perhaps it's just me.
Either way, it was pretty much what you expect from a book like this -- easy to read, slightly cheesy romance, and embarrassingly entertaining.