You could have one for every century. I only have ninety seconds, so we’ll skip a few centuries. In the early church, I love the _Martyrdom of Polycarp_, which is a second-century text. It gives us fresh insight into what was happening in the church at that time. It helps us think about what it means to be a Christian in a culture that is hostile to Christianity. The _Martyrdom of Polycarp_ is the first stop.
Then we’ll skip a bit to the 400’s. We’ll pick up Augustine’s _Confessions_ and Leo’s _Tome_. A “tome” is a big book, but Leo’s _Tome_ is actually only a seven-page letter, so we’ll throw that in.
Later we have Aquinas and his _Summa Theologica_ (13th century). I’ve got a beautiful copy of Latin on one side and the English on the other, but you can find all kinds of versions.
Then we come to the Reformation (16th century). I’m a big fan of Luther’s _Three Treatises_. You have to have Calvin’s _Institutes_, which contains the mature thought of the Reformation after it had been going for a couple decades.
We can skip on to Edwards (18th century). I always tell people that when you read _Religious Affections_, _Freedom of the Will_, or _Original Sin_, you’re at the deep end. Start with the sermons. One of my favorite Edwards sermons is called “The Most High: A Prayer-Hearing God.” It is a beautiful sermon on the doctrine of God and prayer.
Then let’s go to Charles Hodge’s good _Systematic Theology_ (19th century), and then right up to _The Holiness of God_ (20th century). We skipped a few centuries, but it’s enough to get started.