I'd like to nominate Orlando by Virginia Woolf
In her most playful and exuberant novel, Virginia Woolf writes the "historical biography" of Orlando, a young boy of nobility during the reign of Queen Elizabeth I. A wild ride through four centuries, the novel shows Orlando aging, magically, only thirty-six years between 1588 and 1928. Even more magically, he also changes from a man to a woman.
Orlando enters the book as an Elizabethan nobleman and leaves the book three centuries later as a liberated woman of the 1920s. Along the way this most rambunctious of Woolf's characters engages in sword fights, trades barbs with 18th century wits, has a baby, and drives a car. As she explores Orlando's life, Woolf also explores the differing roles of men and women in society during various periods.