In the last decades of the 17th century, the feast of Christmas in Lutheran Germany underwent a major transformation when theologians and local governments waged an early modern "war on Christmas," discouraging riotous pageants and carnivalesque rituals in favor of more personal and internalized expressions of piety. Christmas rituals, such as the "Heilig Christ" plays and the rocking of the child (Kindelwiegen) were abolished, and Christian devotion focused increasingly on the metaphor of a birth of Christ in the human heart. John Sebastian Bach's Christmas Oratorio, composed in 1734, both reflects this new piety and conveys the composer's experience living through this tumult during his own childhood and early career. Markus Rathey's book is the first thorough study of this popular masterpiece in English. While giving a comprehensive overview of the Christmas Oratorio as a whole, the book focuses on two themes in particular: the cultural and theological understanding of Christmas in Bach's time and the compositional process that led Bach from the earliest concepts to the completed piece. The cultural and religious context of the oratorio provides the backdrop for Rathey's detailed analysis of the composition, in which he explores Bach's compositional practices, for example, his reuse and parodies of movements that had originally been composed for secular cantatas. The book analyzes Bach's original score and sheds new light on the way Bach wrote the piece, how he shaped musical themes, and how he revised his initial ideas into the final composition.