The Koestlers' fragmentary, fitfully moving story, 1940-1956: a sensibly edited version (by their literary executor, Harold Harris) of papers found on Arthur Koestler's desk after he and his wife committed suicide in 1983. Part I (1940-51) contains six chapters, written alternately by Arthur and Cynthia, while the six chapters of Part II (1951-56) are all by Cynthia. ""I shall always remain the stranger on the Square,"" wrote Koestler (Montpelier Square in London, where he spent his last 30 years); and the central motif of these unfinished notes is the homeless, restless, driven spirit of A.K. Everything about Koestler seems to have been compulsive: his heavy drinking, his gourmandizing (and forcing his friends to indulge), his Don Juanism (Cynthia patiently endured it), his polymathic curiosity (turning dinners into seminars, as he picked his guests' brains), even his campaign against capital punishment. An exile many times over, uprooted from the Judaism of his birth, the Communism of his 20s and early 30s, from the German or Hungarian-speaking world of Eastern Europe (he remained hypersensitive about his accent), Koestler often made himself and others miserable. But Cynthia (a transplanted South African) loved him, mothered him, and slaved for him through it all. Twice impregnated by Koestler (who had an illegitimate daughter but shrank from fatherhood), she had two abortions, describing them ambiguously as the end of ""a nightmare in slow motion which many couples have experienced."" At the last, she simply could not live without him and overdosed on barbiturates, though she was in fine health and only 55 (to his 78). The main problem with this account is that too much of it is taken up with minor details of A.K.'s literary career: fuming over weak translations of his books, keeping up with his gargantuan correspondence, organizing the Congress for Cultural Freedom, etc. Still, it reads well enough (C.K. has an easy, natural style) and offers some arresting glimpses of an all-too-human genius--amplifying George Mikes' recent memoirs. Arthur Koestler: The Story of a Friendship (p. 247).