Johann Valentin Andreae (1586–1654) caused quite a stir in his younger years as a reformer and writer. Until now, however, his late work has been little known. Research into Andreae‹s extensive literary legacy (preserved by the Herzog-August Bibliothek in Wolfenbüttel) has contributed to clarifying Andreae‹s manifold personas: he was an intense and versatile conversation partner to Duke August zu Braunschweig-Lüneburg; he was also a perceptive observer of the Thirty Year War, a connoisseur and collector of literature, fine arts and music as well as a book lover; but most importantly, Andreae was the leading figure of Lutheranism in southern Germany as well as a follower of Pietism as it was initiated by Johann Arndt. An analysis of this material adds a new dimension to the cultural, intellectual and Church history of the period.