Nigel Nicolson is both biographer and editor. Indeed, Harold Nicolson: Diaries and Letters, 1930-1962 (1966-1968) shows a felicitous combination of those two skills. In reducing his father's diaries from three million words to approximately 150,000, Nicolson performed a demanding feat of selection and compression. The annotations, connecting passages, and correspondence that he inserted between diary extracts ensure that the narrative flows smoothly and effortlessly and that the reader is given sufficient information to follow events. The story told in Diaries and Letters is completed by Nicolson's Portrait of a Marriage (1973). Nicolson had used this title phrase in the introduction to volume one of the diaries, but it was not possible to reveal the full "portrait" while Harold Nicolson and Violet Trefusis still lived. The other literary enterprise with which one associates Nicolson is his coediting with Joanne Trautmann of The Letters of Virginia Woolf, published in six volumes from...