I read it and was disappointed. First of all, Bree isn't a big character to begin with so the whole purpose of a spin off for her didn't make since to me. Second, I found the story a little slow and slightly repetitive. Lastly, though this didn't bother me that much, but it was a little darker than the other livres in the Twilight series, so it didn't have the same feel to it. I would still recommend that toi read it, though. This is all my opinion, so toi might feel different about the book.
It was alright, definalty not better than the main saga in my opinion though. The beginning was slow, and it took awhile to get into, but once there it was quite good. And I agree its darker than the Twilight books. Bree was alot different than how she seemed in Eclipse and how i imagined she would be in this book. I thought she would be plus crazy, ruled par instincts ( I know she is but plus to the 'extreme' :P). Good read, but not as good as any of the Twilight livres (except Breaking Dawn, but that's just because I hate that book with a passion). X