Kierkegaard was driven to write The Book on Adler after news spread that a Danish pastor, Adolph P. Adler, claimed to have experienced a revelation in which Christ dictated a new doctrine. Like many others, Kierkegaard was intrigued by Adler—but for different reasons than most. Over the eight years during which Kierkegaard worked on the manuscript, the phenomenon of Adler became a concern secondary to the larger question of authority. Kierkegaard revised the manuscript many times, and published a segment of it as "The Difference between a Genius and an Apostle" in Two Ethical-Religious Essays, but did not publish the work as a whole before his death. The latest integral version of The Book on Adler is included here, along with excerpts from the earlier drafts and a sampling of writing by Adler himself.