Though he wrote on James Joyce (James Joyce: The Last Journey, 1947) and on the Bloomsbury group, his lifework is summed up in his five-volume biography of Henry James (Henry James: A Biography 1953–1972). Edel discussed the notion of biography in Literary Biography (1957), in particular his conviction that literary biography should enfold a subjective author's self-perceptions into his output. Edel's second and third volumes of the James biography earned him the 1963 Pulitzer Prize for Biography or Autobiography and a National Book Award for Nonfiction in 1963. Edel enjoyed privileged access to letters and documents from James' life housed in the Widener Library at Harvard University, after gaining the blessing of members of James' family.
The discovery of impassioned but inconclusive letters written in 1875–1876 by James to the Russian aristocrat Paul Zhukovski, while Edel was deep in the process of finishing his biography caused an ethical crisis; his decision was to continue to ignore what he considered a peripheral aspect of the self- identified "celibate" and sexually diffident James's life. Edel did treat James's relationships with novelist Constance Fenimore Woolson and sculptor Hendrik Christian Andersen at length, especially in volumes three and four of the biography. After weighing all the evidence, Edel confessed that he was unable to decide whether James experienced a consummated sexual relationship. Although later scholarship and new materials [clarification needed] have called into question the accuracy of his portrait of James, Edel's work remains an important source for studies of the author.
"A biography seems irrelevant if it doesn't discover the overlap between what the individual did and the life that made this possible. Without discovering that, you have shapeless happenings and gossip." — Leon Edel