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.