Citadel of God is set in Italy of the early 6th century. The Roman Empire is decaying. An Ostrogoth king, Theodoric, is marching in triumph to occupy Italy. A young boy, ward of the respected Roman scholar Boethius, rushes in to stab the barbarian conquerer with a stylus in defense of Old Rome and is rescued from death by a young scholar from Nursia who is called Benedictus.

Against this backdrop, the novel goes on to tell of the lives of Boethius, who becomes governor for the king in spite of his patriotism for the dying Rome; Peter, the young would-be assassin and patriot, who grows up to become a conflicted Byzantine ambassador; and Benedictus, who becomes appalled by the corruption in Roman society and retreats into the wilderness to become a hermit. Eventually he founds several monasteries and travels to Montecassino. He drives out pagan sorcerers, works miracles and founds a monastery that truly became a "Citadel of God" that stood against paganism and Arianism, while the scholar Boethius is jailed and executed by the increasingly paranoid king, after writing The Consolation of Philosophy.

This book is strongly and vividly written, telling an epic tale of several famous lives intertwined during this unstable and critical time in the history of Christendom. The reading and interest level are suitable for ages 14 and up; however, the emotional maturity level may be somewhat higher. There are a couple of scenes, as when a Roman lady tries to seduce the young Benedictus, or a corrupt Christian priest converses with his mistress, that though not overly graphic might be unsuitable to some young readers.

St. Benedict (480-543), particularly honored as the Father of Monasticism, is an essential character in understanding Christian Culture as it existed in the Middle Ages because it was heavily influenced by the Monasteries (and the rule of St. Benedict) which helped to preserve Catholicism and classical learning after the fall of the Roman empire. Fortunately, this particular book is very simple and aims at telling the STORY of St. Benedict. The author introduces us to his spirituality, the realm of his influence during his own lifetime, and in a very real and tangible way, how the devil tried to fight the good God did through this holy monk. Like all good saint stories aimed at children, the author provides us with a real, live, interesting person, actively engaging our attention and causing us to want to imitate him. (Make no mistake, even though it's aimed at children, it can have the same effect on their parents too.) The story provides excellent supplemental material to a history program as it also covers some of the major political and social events of the times through the eyes of St. Benedict. Our family found the story and the interest level suitable even for the little ones, although the reading level is harder to determine. Kolbe Academy recommends it for 7th grade (based on length) and Seton Home Study recommends it for 6th grade.