Fans of the show will enjoy getting new insight into the minds of the characters before the show started. You know the outcome but the fun is in seeing how all the characters got to where they ended up. It is also interesting to get inside each character's head and hear their own perspectives on what is going on in their lives. While it does provide enough information for those who haven't seen the TV show, I believe fans of the show will pick up on more throughout the book.
Overall, fans of the show should definitely pick up the book. It will be a fun and enjoyable read.