This is not terrible, but I don't understand the motivation. Jess is the physical twin of her cousin Freya, who has died. I don't understand WHY Jess is so obsessed with Freya's death when there is no reason to believe it was foul play.
Both Freya and Jess are very dull characters. I believe this book is trying to summon the "Rebecca" feeling, of the mysterious, seductive deceased. It's not working.