"Rosemary and Rue" is the first book in the October Daye series by author Seanan McGuire. It follows the story of October Daye, a half-fae, half-human private investigator who becomes embroiled in a murder mystery within the faerie realm. After being turned into a fish for years, she returns to find her life has changed dramatically. The novel explores themes of identity, loyalty, and the complexities of the faerie world. As October navigates her challenges, she encounters various supernatural beings and uncovers dark secrets that threaten her and her loved ones.