Island Realm - Crystal Doors, #1

What happens when your father accidentally transports you through a magical doorway? From New York Times bestselling authors Rebecca Moesta and Kevin J. Anderson Fourteen-year-old cousins Gwen and Vic have lived together ever since the mysterious deaths of Gwen's parents and the disappearance of Vic's mother. When Vic's scientist father accidentally transports them through a magical doorway to the island of Elantya, the challenges begin. Elantya-wonder-filled place of magic as well as steampunk technology. Vic and Gwen are soon caught in a tempest of ancient magic, bizarre gadgets, vicious creatures, and fierce battles in a territorial feud with the sea-dwelling merlons, an age-old conflict between the bright and dark sages ...
and Gwen and Vic's own mysterious roots.