James Ussher achieved the highest ecclesiastical office available in his native Ireland, serving as archbishop of Armagh from 1625 to 1656. His service to the English monarch and to the English church in its Irish guise was protracted and distinguished. Ussher's situation was both singular and complex. Heading the Irish Church at a time when the English Protestants he represented were a minority compared to the native Irish and English Catholics, Ussher presided over a church in which many of the ministers were actually Scottish. Nevertheless, Ussher earned the respect of men of all religious persuasions. At the same time his reputation as a man of letters, an erudite theologian and historian, spread throughout Europe. Consumed by a need for books and manuscripts to support his research, Ussher accumulated a vast collection of materials. The vicissitudes of his library, which was caught up in the tragedy of civil war, surpassed...