A. J. Cronin was a Scottish author and physician, born on July 19, 1896, in Cardross, Scotland. He is best known for his novels that often explore themes of social justice and human compassion. His most famous work, The Citadel, published in 1937, highlights the struggles of a young doctor and critiques the medical profession. In addition to his literary contributions, Cronin served as a medical officer during World War I, which influenced his writing. He also wrote several other notable works, including Hatter's Castle and The Keys of the Kingdom, which further established his reputation as a significant figure in 20th-century literature.