"On the Apostolic Preaching" is a recently discovered work of Irenaeus, a second century theologian. Irenaeus is better known for his attacks on Gnosticism but he still has time to write a summery of the Christian faith for his friend Marcianus.
In his book, Irenaeus presents the faith chronologically, from the creation of the world to the death of Christ. He masterfully interprets the Old Testament to show that Christ is the focus and the culmination of the Old Testament. When he does this, he is also attempting to refute a common Gnostic belief that the old bloodthirsty God of the Old Testament was a completely different creature from new gentle God of the New Testament.
He continues and finds support in the Old Testament for nearly every aspect of Christ and for the actions of the Apostles. This book also contains one of the earliest explanations of the Trinity which is interesting to see how it compares to modern understanding on the subject.
This book is a fascinating glimpse into the mind of a second century theologian and an interesting read.