I've read a lot of vampire books, and while taken at face value it would seem that Sunshine is another vampire book, those looking for a typical vampire romance or Buffy-type book will be disappointed, if they even get through Part 1. 
 The whole book is the internal struggle of Sunshine - meaning while there is action and dialogue, the book resembles more of a stream-of-conscious style that can take a bit to get into. It is a fairly long book, and most of it is Sunshine's thoughts, fears, and "coming to terms" with who she is and what she has to do. The action of the story, the resolution of the conflict, and the relationships between the characters are important to her realization, but play more of a supporting role. This leaves a lot of questions unanswered, questions that in other books would have been answered, or would have been fodder for book 2, but that is not the case here. 
 I wasn't really invested in the book until I started Part 2, but I was glad I did. Sunshine is not your typical book, but it slowly drew me in, and while I can't say I was satisfied by the ending, it was enough. I liked that it was so different from what I usually read.