John Barleycorn is a classic autobiographical novel/alcoholism study by Jack London. This fascinating book bears witness to Jack London's own experiences with alcohol. London, who had been acquainted with alcohol from his youth, comes out boldly against John Barleycorn. The book relates a string of exciting adventures, yet it makes its point nonetheless.The novel's themes include masculinity and male friendship. London discusses various life experiences he has had with alcohol, and at widely different stages in his life. Key stages are his late teen years when he earned money as a sailor and later in life when he was a wealthy, successful writer.Alcohol plays a big role in facilitating the themes listed above.