The God's Wolfling — Cedar Sanderson

When The God's Wolfling opens Linnea Vulkane has grown up since the summer of Vulcan's Kittens. Sanctuary, the refuge of immortals on an Hawaiian island, is boring. When the opportunity for an adventure arises, she jumps right into it, only realizing too late the water may be over her head. Literally, as she is embroiled in the affairs of the sea god Manannan Mac'Lir. Merrick Swift has a secret he's ashamed of. Then when he meets Linnea and her best friend, he doesn't like her. She's bossy, stuck up… and oddly accepting of his wolf heritage. Like her or not, he must do his duty and keep her alive. The children of the myths are being plunged into the whirlpool of immortal politics, intrigue, goblin wars, and they might be the only ones who can save a world.