New York

Author, historian and British peer John Julius Norwich has never displayed any lack of drive and energy, but even by his standards, “The Popes: A History” (also published as “Absolute Monarchs: A History of the Papacy”) is ambitious in the extreme.

Crammed into its pages are the lives of 265 popes, from St. Peter to today’s Benedict XVI, their struggles with challenges to religious orthodoxy as well as battles with secular powers ranging from Frederick Barbarossa to Communism.

Religious scholars may find little to love since Norwich devotes more time and attention to the notable figures of the papacy and less to early figures like Pope Dionysos or Pope Zephyrinus, despite the latter’s 18-year tenure in the second century.

Critics within the Catholic church may look with disfavor on Norwich’s occasional bursts of irony and deadpan humor, his critical evaluation of the zealous canonization program embarked on by the late John Paul II and his outright disgust at the excesses of the Church and its leaders.

For the general reader, this is an admirable, lucid and often entertaining tome — and one that manages to be respectful, despite having been penned by a self-described Protestant with little religious conviction.

Norwich revels in tiny details that betray the spirit of an age, such as the medieval pope who banned physicians from treating patients who weren’t in a state of grace. But his race to cover the most important trends and events means there are tiny errors, such as inaccurate dates for the guillotining of Marie Antoinette and Mussolini’s lynching.

Norwich’s scholarly knowledge of the earlier centuries — as the popes struggle with the Byzantines and the Norman kings of Sicily — may be what makes those pages feel more compelling than his discussion of the Vatican in the 18th and 19th centuries. There are also elements that are missing altogether, such as any reference to the debates over liberation theology.

Norwich’s history shows that until very recently, the Church’s instinctive approach to rival faiths or sects has been to crush them. He chronicles the Crusades and the 1204 sack of Constantinople, from which that once-great city never fully recovered. Norwich chronicles the Vatican’s insistence on its monopoly over revealed truth and its harsh response to challenges, whether these came from the Protestant churches or from within the fold.

It wasn’t until the late 20th century that ecumenical views gained ground within the Vatican. Pius XII’s “hands-off” approach to the Holocaust, even when he could almost literally watch Italian Jews being rounded up from his windows in the Vatican, was one of the last signs of the old attitudes, Norwich writes. John Paul II, a pope who saw Communism as far greater a threat to the souls of humankind than other religions, oversaw the first major ecumenical initiatives.

Norwich believes Benedict XVI has displayed less diplomatic prowess than his predecessor, offending a number of other religious groups, including Jews and Muslims, by remarks made since his election to St. Peter’s throne in 2005.