At the end of the day this book is first and foremost setting the scene for future books in this series and there's nothing wrong with that. I give the author Heather Linn some real kudos for the twists she had in her plot. I certainly didn't pick them all. The end of the book set things nicely for the next book.
Author Linn has an interesting, almost conversational writing style, which I think probably appeals to her target market. I personally felt that some more attention to editing and layout could well have improved the readability of the book. There were also the requisite number of typos and word errors that one has come to expect from self-published books (which I'm assuming this is) but I have made a point of never letting that detract from my reading of the story.
I enjoyed this book far more than I thought I would once I got past the first chapter. I might even have considered 5 stars, instead of the four I gave it, if the layout and editing was better and perhaps my only real gripe - the dialogue. I did feel the dialogue was stilted in places. The reality is people do talk in contractions and author's have to accept that and write their dialogue that way.
Look, this is a novel concept for a plot, it was well constructed and basically just an enjoyable little read. If you're a vampire fan, then this is a new take on an old theory. Give it a go!