Books: 20th Century Pepys

HAROLD NICOLSON: THE LATER YEARS, 1945-1962, VOL. Ill OF DIARIES AND LETTERS. Edited by Nigel Nicolson. 448 pages. Atheneum. $8.50.

When Sir Harold Nicolson died last May at 81, enfeebled by age and prolonged illness, he was only vaguely aware that the first two volumes of his diaries and letters had brought him a quality of fame that had eluded him all his life. Perhaps the knowledge that he was being hailed as a Pepys to his age and peers might have struck him as an odd and final irony. "To be a good diarist,"...