Summary: For me, it wasn't even the summary that sold me on this book - it was really the cover. Every time I stepped into the bookstore, this cover popped out. It's unique and unmistakable on the shelves with rows and rows showing cut-off torsos of teenage girls on brightly colored covers. Prophecy of the Sisters looks dark, and the story is dark.
The book is set in the late 1800s and follows Lia Milthorpe right after the death of her father (and a few years after the death of her mother) - each parent dying with mystery shrouding the real causes. Lia, her twin, Alice, and their wheel-chair-bound younger brother, Henry, are left in the care of their Aunt Virgnia. Lia becomes friends with a girl from school, Luisa, and a young spell-caster/fortune-teller, Sonia. Each of them play a part in the little-understood Prophecy of the Sisters, but mainly leaving Lia on the good side of the story, with Alice on the opposite.
The Prophecy itself basically says that two sisters (obviously Lia and Alice) will battle for the outcome of whether Samael (the evil-overlord of the Souls) can enter their world and reign with his evilness. One sister is the Gate that will allow Samael to come to power, the other is the Guardian who must try and keep the Gate closed. The regular concepts of these roles have become confused with the birth of Lia and Alice - much of the shock and surprise comes from Lia's continued understanding of what the Prophecy truly means and exactly how much of her life and the past has been affected by this Prophecy.
The cover-summary does mention "a boy" who, within the first few pages, is known to be James (the son of a family friend and the love-interest of Lia). With this mention on the all-powerful Flap-summary, I was expecting a bit more action from this character... maybe that's just what reading so much YA literature has led me to prepare for. But if you're looking to read this book for a little bit of romance, you will be disappointed. Sure, there are some cute scenes, but Zink focuses the story on the sisters, their choices, and the Prophecy that surrounds their lives - she doesn't put any fluff in, which is a great thing. I did ask Zink about James when I met her at TAC (the Teen Author Carnival on May 24th in NYC) and she explained that we shouldn't count him out of the story all together. He'll be back :)