IN 1958, Aged Seventy-Six, Angelo Giuseppe Roncalli became supreme leader of the Catholic Church, assuming the name John XXIII. Neither a well-known public figure nor a highly trained theologian, he was initially regarded as a transitional pope. But he would soon prove to be much more, awing the world with a deep concern for the plight of humankind. Set within the sweep of two thousand years of papal history, bestselling historian Thomas Chaill follows the life of a man who rose from peasant origins to scale the pinnacle of religious power - and who used that power in the Second Vatican COuncil to revolutionize the Church's relationship to our world.