In this limpidly written, absorbing text, British historian Marsden recreates the vanished world of Celtic Christianity and the devastating impact upon Hiberno-British monasticism of the first Viking raids. ``From the fury of the Northmen, O Lord, deliver us,'' prayed the monks of Ireland, England, and Scotland during the early Viking Age. Irish monasticism spread rapidly in the British Isles from the sixth through the eighth centuries. Marsden begins his account with the disastrous raid on one of the holiest monasteries of all, the church and shrine of St. Cuthbert on the island of Lindisfarne in 793. Marsden indicates that this first recorded attack upon a Celtic monastery by the pagan Norsemen shook the Anglo-Saxon and Celtic civilizations to their foundations, as churchmen asked whether the Lindisfarne raid presaged further scourges at the hands of an angry God: ``What should be expected,'' the great Northumbrian scholar Alcuin asked in anguish, ``for other places, when the divine judgment has not spared this holy place?'' A similar fate befell monasteries on Inishmurray and Inishbofin, I-Columcille on Iona, and Inis Patraic, among other places. The escalation of such raids over the next 30 years and the waves of Viking settlement that followed them ultimately transformed Irish and British society, little changed from the time of St. Patrick four centuries earlier. By the time the great Anglo-Saxon king Alfred of Wessex checked Viking rule in England in the late ninth century, Norse customs, names, and place names had become commonplace in British and Irish society, while the descendants of the Northmen, Christianized and settled, became assimilated and absorbed into the Irish and British populations. A fascinating look at a transformative event in the history of the British Isles.