Guardian of the Gate - Michelle Zink

Sixteen-year-old Lia Milthorpe must journey to the uncharted isle of Altus to continue her search for the missing pages of the Book of Chaos - the pages that could tell her how to end the prophecy that has turned generations of sisters against each other. But the journey will test more than just her courage, it will also test her loyalty to her beloved boyfriend, James.

Meanwhile, twin sister Alice will stop at nothing to reclaim Lia's role as the Gate. And that's not the only thing she wants from her sister: there's also Lia's true love.

The outcome of their battle could have consequences of Biblical proportions and, in the end, only one sister will be left standing.