Gelb, Arthur, and Barbara Gelb.O'Neill. Harper, 1962, 1987. Reliable biography based on interviews with the playwright's friends.
Manheim, Michael.Eugene O'Neill's New Language of Kinship. Syracuse University Press, 1982. Traces the development of O'Neill's understanding and expression of tragedy.
Ranald, Margaret Loftus.The Eugene O'Neill Companion. Greenwood, 1984. Reference guide to all aspects of O'Neill's work and life.