But why would anyone want to read City of God? According to Collin Garbarino:
Because it’s awesome. Augustine of Hippo started his magnum opus after Germans sacked the city of Rome in 410. Both pagan Romans and Christian Romans took the destruction of the city pretty hard, and both looked for meaning in the event. The pagans blamed the Christians, and many Christians couldn’t understand how this catastrophe could happen in a Christian empire. Augustine writes his book to put historical events in a theological perspective. City of God has everything—history, theology, philosophy, science. Augustine crams a lot of ancient learning into this one book. I like to think of the City of God as the capstone of the ancient world. It’s definitely worth reading.My own answer would be that, quite apart from its importance for understanding Augustine and its more general theological importance, it is one of the seminal works in the philosophy of history.