Island Realm — Kevin J. Anderson; Rebecca Moesta

Fourteen-year-old cousins Gwen and Vic have lived together ever since the mysterious deaths of Gwen's parents and disappearance of Vic's mother -- until Vic's scientist father accidentally transports them through a magical doorway to the island of Elantya, a 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.