Lana Ferguson’s “The Nanny” is a seductive book about modern romance. Cassie Evans, the main character, is facing homelessness and impending eviction. She gets hired as a nanny for chef Aiden and his daughter. She quickly learns, though, that Aiden, who has been using her OnlyFans account for a while, might be her biggest fan. Cassie is trapped in a tornado of feelings and choices as she works through this unexpected turn.