Well, a sleepwalk novel might be a type of fictional work that focuses on the psychological aspects of sleepwalking. It could explore how the mind works during sleepwalking, perhaps with a scientific slant. The story could revolve around a sleepwalker who discovers something about themselves or their past while in that sleepwalking state. It could also be a horror - themed novel, where the sleepwalker does things that are terrifying, either to themselves or others.