In 1962, a few years before his death, Sinclair published his view of his long life and many accomplishments in The Autobiography of Upton Sinclair (Harcourt, Brace). While The Jungle and the social changes that resulted from it are clearly the most notable accomplishments in his life, his life was filled with other publications and deeds that make it notable, including the founding of the American Civil Liberties Union and breaking the Rockefeller oil trust with his novel Oil!.
Leon Harris' biography Upton Sinclair: American Rebel, published in 1975 by Thomas Y. Crowell Company, is a thorough picture of the author's life. It paints a generally positive picture of the author's life, a picture that his critics might find a little too rosy.
Theodore Dreiser's book Sister Carrie was published a few years earlier than The Jungle, in 1900. It shocked readers of the day with its grim realism and frank sexuality, presenting what might be the best example of the realistic style that Sinclair used to make his social message powerful. Dreiser's later and more famous book, An American Tragedy (1925), about a famous murder in Chicago, also reflects Sinclair's style and social concerns.
James R. Barrett's book Work and Community in The Jungle: Chicago's Packinghouse Workers, 1894-1922 is an explanation of the social situation that Sinclair wrote about. Published in 1987, this book makes an excellent companion piece to The Jungle, and was published along with the authoritative 1988 version of the novel (for which Barrett wrote the notes) by the University of Illinois Press.
Emile Zola is considered the father of the Realist movement, and was certainly one of the most dedicated social critics to ever write novels. Much of Sinclair's style can be seen in the work of Zola. Almost all of his books are considered classics and are read today, but in particular The Dram Shop from 1877, concerning alcoholism, might interest Sinclair readers, since it is a theme that is visited frequently in The Jungle.
Another follower in the Realistic vein was James T. Farrell, who wrote a trilogy of books about an Irish-Catholic boy growing up in Chicago. The books were published throughout the 1930s, and then collected together in 1938, in a volume called Studs Lonigan, with a new introduction by the author.