Casparian, Gregory
"An Anglo-American Alliance: A Serio-Comic Romance and Forecast of the Future" by Gregory Casparian is a novel published in 1906. Set in 1960, it envisions a world where two upper-class women from Britain and America meet at a ladies' seminary and develop a secret romance. Their relationship takes an unexpected turn when one undergoes surgical transformation to become a man. This obscure work has been called the first lesbian science fiction novel and features what may be science fiction's first transgender hero. (This is an automatically generated summary.)
These books are free to read. Each is in the public domain in the United States; check your own country's rules before you copy or share one.