Johann Arndt’s True Christianity was the most popular devotional work within the Lutheran tradition in the century following the Reformation. This book went through a number of editions in Germany, and has been translated into dozens of languages. Through a series of meditations, Arndt discusses the Christian life in practical terms, which were meant to be understood by the average layperson.
Arndt’s writing was influenced by the Theologia Germanica, John Tauler’s sermons, and Thomas A Kempis’ The Imitation of Christ, along with the writings of Martin Luther. Significantly, Arndt mentored Johann Gerhard, who continued Arndt’s promotion of practical piety, while also providing a rigorous academic defense of Lutheran thought.
The Church: Its Origin, Its History, Its Present Position by Luthardt, Kahnis and Brückner (Classics in Dogmatics)
The Augsburg Confession with a Historical Introduction and Notes by Charles Krauth (Lutheran Confessions)
Annotations on Ephesians, Philippians, Colossians, and 1 and 2 Thessalonians (Lutheran Commentary Series)