THE WORLD of Jack and Rita Leddy is not about greatness but about goodness, not about great goodness but about genuine goodness. This is why it bears retelling, 11 writes Mary Jo Leddy in Memories of War, Promises of Peace (Lester & Orpen Dennys, 170 pages, $22.95 cloth). Jack and Rita Leddy -- he a doctor, she a nurse -- committed themselves to the Allied war effort in July 1941, just a month before their marriage. By July 1944, Jack was working at a casualty clearing station in France while Rita nursed in England. After the war, Jack remained in Britain to complete his surgical training and in 1947 joined Rita in Canada, where they settled in Saskatoon and became, to the unenlightened eye, a typical Canadian family. Something set the Leddys apart, however, and when Mary Jo read her father's wartime diary, she understood at last what it was. While others had agonized over the war, her parents had made personal sacrifices that helped to end it. Their work as "menders of the world" deserves to be remembered; this book, which links the Leddys' recollections with their daughter's commentary on responsibility, social justice, and future survival, accomplishes just that.