WORK CREWS in Europe excavating foundations, dredging channels, and building new roads still come upon bodies from World War I. Coping with the British and Commonwealth share of that grisly harvest has been the work of the Commonwealth, War Graves Commission since its founding in 1915.

Courage Remembered (McClelland & Stewart, 282 pages, $29.95 cloth) is a history of the work of this body and a guide to the monuments it tends. G. Kingsley Ward and Major Edwin Gibson, the authors, approach their task with the same sober, meticulous care the commission itself has applied to the work of locating, identifying, and commemorating the 1,750,000 Commonwealth citizens who died in the two world wars.

More than 200,000 lie in graves marked "known unto God," a phrase from Kipling. The reason many of the commission's 2,500 cemeteries have huge memorials is not to glorify battle but to provide enough wall space to inscribe .the names of all those whose bodies were never identified.