Emily Windsnap and the Falls of Forgotten Island (#7) by Liz Kessler

While on vacation, Emily Windsnap finds herself swept up in an ancient prophecy as the New York Times best-selling series continues.

Emily is headed to a tropical island for a relaxing vacation with friends and family. And this time, Emily promises her best friend, Shona, there will be absolutely no adventure — just plenty of fun. But somehow excitement always seems to find Emily, and before she knows it, she ends up on the other side of a powerful waterfall on a forgotten island no one else can get to. Well, no one that isn’t a half-mer like Emily and her boyfriend, Aaron. The people who live on the island believe in a prophecy that foretells how they can be saved from an imminent, devastating earthquake — and this prophecy seems to revolve around Emily and Aaron, as well as a mysterious, mythic giant. Will they be able to find the giant — and fulfill the prophecy — before it’s too late?