For anyone interested in the history of private auricular confession in the early days of Lutheranism, I highly recommend the book The Reformation of the Keys: Confession, Conscience and Authority in Sixteenth-Century Germany, by Ronald K. Rittgers.

I wrote a review of this book for Comitatus (Vol. 36), but copyright prohibits me from just pasting the whole review here. I think it will be okay if I just paste the first and last paragraphs, however...

In the historiography of the early Reformation, various theological loci have been treated exhaustively. Justification has always received the most attention, with the sacraments and ministry following close behind. Confession and absolution have, however, received scant attention, except insofar as they relate to justification. In The Reformation of the Keys, Ronald Rittgers seeks to fill this void. Using a pleasant prose style unencumbered by some of the jargon associated with too much work on social discipline, Rittgers details the transformation of confession and absolution from its medieval penitential forms into a new evangelical tool for the consolation of the sinner’s conscience. His particular focus is on the imperial city of Nürnberg, where the adoption of the new evangelical form of absolution followed a different path than that of other cities that adopted the Reformation early on.

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While Rittgers does steer clear of messy jargon, the reader will need to know the various theological categories of Lutheranism to get the full meaning of Rittgers’ work. He does not stop to define terms such as “Two Kingdoms” or “Law and Gospel,” which are heavily loaded terms in Lutheran theology. This however is not a short-coming of the book; only a warning to the casual reader to come prepared to a well-documented and thoroughly grounded discussion of a key moment in the development of Lutheran theology.

Rittgers, FWIW, was a student of Steven Ozment at Harvard, who is among the best and brightest of Reformation historians today. Rittgers' book promises that he will follow in his doktorvater's footsteps.