The Epistles of Ignatius (free text, free audio)
Why don't evangelical Christians study these historical texts more? There seems to be something taboo about quoting the early church fathers, yet nothing taboo about quoting 20th century sources, Puritans, or whomever else after, say, Calvin. These epistles from Ignatius Bishop of Antioch to the churches at Ephesus, Magnesia, Rome, Smyrna, Philadelphia, Tralles, and to fellow bishop Polycarp are great history. If you've ever asked "what happened next?" while reading Paul and Peter's epistles, read Ignatius.
I believe these works also help in determining whether we're interpreting a New Testament text correctly. How does Ignatius quote from the gospels and epistles? He's writing to Ephesus and others after Paul, Peter, and John did, knew their strengths and weaknesses. Ignatius is writing from Syria (Antioch). He came to be Bishop of Antioch around 67 A.D. knew Polycarp, would have known John and was likely discipled by him. He died a martyr in 108 A.D. Ignatius was the first to use the word "catholic" for the universal
church, which was later given a capital "C" and that makes Protestants today uncomfortable.
I find Ignatius continues the concern found in Peter and Paul's epistles for orthodoxy. Ignatius comments on the eucharist, the body and the blood, remind many of transubstantiation and makes them uncomfortable. Without a commentary, I see him referring more to the danger of gnostic influences who denied that God took on flesh. I also am reminded that the order of succession was important to the early church; if you didn't get your teaching from either the circulating gospels or epistles, or from someone who knew and got their commission from the Apostles, then it was in error. I think this sheds light on his exhortation not to take the eucharist or be baptised apart from an elder.
He has similarly strong Pauline and Johannine concern about the influence of Judaizers: "For Christianity did not believe in Judaism, but Judaism in Christianity."
Ignatius wrote these epistles rather hastily, likely on his way to martyrdom. For early Christians, that was just a given reality-- Jesus, his disciples, and the next generation expected and met that end with joy and peace. But Ignatius wanted them to meet it holding fast to the right gospel as well.
"I am God's wheat, and I am to be ground by the teeth of wild beasts, so that I may become the pure bread of Christ."