Chemnitz's Works, Volume 10 (Apology of the Book of Concord)

After Martin Luther's death, many theological issues were addressed in the Book of Concord in 1580. A mere three years later, a defense of the Book of Concord was required in order to refute attacks on the theology presented there-thus the Apology of the Book of Concord was written.
Martin Chemnitz, Timothy Kirchner, and Nicolaus Selnecker prepared this project, clearly presenting the theology of the person of Christ and the Lord's Supper in addition to defending doctrine.
As Friedrich Bente said, "Alongside the Formula of Concord, there is no other book of that period in which the pure doctrine of the Lord's Supper, the person of Christ, and original sin, along with related doctrines, is presented so clearly and convincingly and defended against the objections of the false teachers."