Sinclair’s first and greatest success was her novel The Divine Fire (1904), promoting the idealistic philosophy of T. H. Green, who believed that it was man’s duty to realize his divine nature by becoming more conscious. Self-development was a fundamental imperative for both Green and Sinclair. In her succeeding works, however, she abandoned the mechanical tone of moral elevation that marred The Divine Fire for a more realistic style. Her creative powers seemed to have been released by the critical work she did on the Bronte novels, The Three Brontes 1912). The Three Sisters tempers her enduring idealistic and mystical interests with psychological realism, using the psychoanalytic theories of Sigmund Freud. While The Divine Fire was her most popular novel, Sinclair’s best novels are The Three Sisters and the autobiographical Mary Olivier: A Life (1919). In her later work, she used ideas of Freud and Carl Jung, imagism, and the stream-of-consciousness technique to suggest the co-existence of idealistic and naturalistic drives. She was controversial for her choice of subject matter—for example, the frank treatment of feminine sexuality. Her later novels and short stories are not generally believed to be as good as those in her fertile middle period (1914-1919).
Her work has been neglected by critics, but feminist criticism is reviving interest in May Sinclair as an important transitional figure in the modern novel. She was on the leading edge of novel technique after World War I and was known as a sensitive critic and a champion of young artists such as T. S. Eliot and Ezra Pound. Critics, however, still do not agree on whether she was an imitator or an innovator in technique. Her work has affinities with that of Dorothy Richardson and Henry James in terms of the theme of self-development and use of limited narrators; with George Bernard Shaw, Samuel Butler, and H. G. Wells in terms of stream-of-consciousness; and with D. H. Lawrence in her treatment of sexual themes.