Forevermore by Cindy Miles
Ivy's moved to her new stepfather's cold castle in the wilds of Scotland, where strange things begin to happen: the ancient walls spilling their dark secrets. Rescue comes when she meets Logan, a gorgeous, elusive boy - a ghost, who has haunted the castle grounds for decades. Ivy is immediately drawn to him . but Logan is not the only spirit around, and soon Ivy finds herself at the heart of a dangerous mystery.