Each term in the title of this book requires some explanation.
Printing takes the pride of place because this book deals exclusively with printed material and with the fact of printing itself, the technology and its limitations and constraints, and what historians may be able to make of it and them. This study depends in no small part on what was printed, where, who may have read it, and how it may have been understood.
This is also a book about propaganda in that it is a study of persuasive literature that attempted to redefine a major institution in its social world: the Christian church and its beliefs. I argue that the medium of printing was used for the first time in Western history to channel a "mass" movement to affect change concerning this institution. By using mass I do not mean that the whole or even a majority of the population were directly targeted by Reformation propaganda. The majority of the population were at best spectators at this drama, affected but unengaged except, perhaps, for the Reformation's unwelcomed offspring, the German Peasants' War of 1525. I do mean that printing was used to reach an audience far larger than any previous movement reached and one that could not have been reached as quickly and as effectively before printing's invention. Those members of the reading public engaged by the Reformation publicists, or at any case a significant subgroup of them, in turn shared these views orally with a much larger group. Together they inspired the Reformation movement.