What Maisie Knew is a 1897 novel by American/British author Henry James. The story was first published in The Chap-Book and the New Review, two prominent American literary magazines of the time.
The titular protagonist of the book is Maisie, a young girl whose parents have divorced each other. The book follows her growth and development over the course of many years, as she evolves from a little girl to a more mature, sensible teenager. Maisie has a difficult upbringing, as the book chronicles, for her parents use her as a tool to express the vestiges of their frustrations from a bad divorce by extracting revenge on the other. Eventually, her parents abandon her entirely, and Maisie must make a tough choice about which of the guardians in her life she wants to put herself in the custody of.
What Maisie Knew is an extremely influential piece of American literature, analyzed by many scholars and critics over the years. Maisie's psychological growth has been a prominent subject of study; a few scholars point to her as a paradigm of Freudian developmental psychology. The book was also adapted into a successful movie in 2012.