(This is a re-post of an entry from when I was using blogspot. It is now archived here.)
Have you read The Epistle of Mathetes to Diognetus? It is basically a letter like the Pauline Letters in the Bible (Galatians, Colossians, etc). We don’t know who wrote it; it’s not part of the Bible, but it is one of the earliest Christian works that apply the use of apologetics in writing to defend Christianity. Contents include the topics of manmade idols, the difference between the Jews and the Christians, and Jesus coming to the world. Here is a link to it if you want to take a look (It’s not that long, only 12 short chapters): http://www.earlychristianwritings.com/diognetus.html