Actually, it was a combination of the writings of Saints Ignatius, Polycarp, Irenaeus, and Justin Martyr with honorable mention going to Eusebius’ History of the Church.
St. Ignatius and St. Polycarp were the first I read, because I downloaded from the internet everything they wrote immediately upon hearing about them. That was almost five years ago now.
Marvellous — you know, I think we catholics do not teach our young enough. The writings of the early Christians should be mandatory during confirmation