Thus far one of the best books I've read this year is The Unquenchable Flame by Michael Reeves. If you only have time to read one book, read the Bible. If you have time to read two books, read more Bible. If you can squeeze a third in read Reeves' highly accessible and winsome introduction to the history of the Reformation. I heartily agree with Mark Dever who wrote the foreward that this book is "The best brief introduction to the Reformation I have read."
Follow THIS LINK to view the website for the book that has gobs of resources to read and listen to for further study of the subjects addressed in this book. Below is an excerpt from the book (which comes in under 200 pages) that addresses "How to reform a church" (pgs. 56-57):
"Luther... instead of using force to reform, sought to persuade people with the Scriptures through simple, clear preaching. He believed that the word of God must first convince people, and then the rotten old structures would collapse. It was exactly what he had stood for before the emperor, that it is the Scriptures that must drive and dictate thought and practice. As a result, Luther never believed that he should devise any great programme for spreading the Reformation. He simply wanted to unleash the word of God, and let that do all the work."