What we all know about Freud is that he said it’s all about sex: Oedipus and Electra complexes, penis envy, and dreams that, when properly interpreted, are juicier than a Jackie Collins novel. Of course, that’s a grotesque oversimplification. Freud also wrote extensively about death, although “extensive” is not the word for “On Transience,” the tiny 1915 essay that inspired Matthew von Unwerth’s somewhat larger book, Freud’s Requiem: Mourning, Memory, and the Invisible History of a Summer Walk. At roughly 1,000 words, Freud’s meditation touches on beauty, loss, grieving, and renewal, with explicit reference to World War I. It also mentions two friends with whom he took a walk, although not by name. These were, apparently, poet Rainer Maria Rilke and his former lover, psychoanalyst Lou Andreas-Salome, whose life and loves have inspired writers of both fact and fiction. Von Unwerth’s book follows Freud to his 1939 death, with discussions of his frequent strolls, his acceptance of decay, and his love of dogs. The father of psychoanalysis last used the word “transience” in his translation of Topsy, Freud follower Marie Bonaparte’s biography of her Chow Chow, the first dog ever to receive radiation therapy for cancer. Topsy, who recovered after much the same treatment that failed to save Freud, “is wiser than I,” wrote her owner, because she “simply inhales the scented June air.” Ultimately, Freud chose neither Rilke’s gloom nor Topsy’s obliviousness, but rather a familiar theme: People who desire enduring legacies have “a surplus of unsatisfied libido.” Von Unwerth reads at 1 p.m. Sunday, Oct. 9, at Politics and Prose, 5015 Connecticut Ave. NW. Free. (202) 364-1919. (Mark Jenkins)