In Sempre Susan, her very charming, recently released memoir of life with Susan Sontag, Sigrid Nunez—she was the girlfriend of Sontag’s son, David Rieff, as well as the grande dame’s youthful assistant—gives us a taste of the master’s esprit. “To read a whole shelf of books to research one twenty-page essay,” Nunez writes, channeling Sontag, “to spend months writing and rewriting, going through one entire ream of typing paper before those twenty pages could be called done—for the serious writer, this was, of course, normal. And, of course, you didn’t do it to feel good about yourself. … You didn’t do it for your own enjoyment (unlike reading), or for catharsis, or to express yourself, or to please some particular audience. You did it for literature.”