Among many things, he notes
It is inevitable that the anniversary of the Reformation would bring forth a flood of new publications. “Martin Luther: Renegade and Prophet” is undoubtedly one of the best and most substantial. Deeply researched over a period of more than 10 years, this biography offers a fresh and deeply illuminating study of the man who somewhat reluctantly divided a continent. What emerges is a work of impeccable scholarship and painstaking fairmindedness. In particular Roper has mined the correspondence, which illuminates every page of this book, as Luther coped with the strains of first becoming a public figure, searched for allies and unburdened himself to trusted friends. In letters that were both deeply learned and alarmingly frank, his charisma shines through, but we also see his complexity: He was a man who could, by turns, be abusive and utterly unforgiving, but also gentle, affectionate and funny.
Roper is especially good on Luther’s unusual upbringing as the son of a mining family. It was a hard life, full of risk; they lived well, but always one bad business decision away from disaster. Young Martin knew that the price of his education was an investment in the family’s future, and how much his decision to abandon his legal studies in favor of a church career would disrupt his father’s plans. But any breach between the two healed, and Luther rose steadily through the ranks of the Augustinian order. His appointment as professor in Wittenberg was at first unwelcome; Luther felt he had been exiled to a provincial backwater.
And he concludes
… but the focus on Luther’s inner life leaves us with an incomplete sense of how the man became a movement.
I agree in large part with Pettegree’s assessment and his summary of the volume is superb. But Roper has really delivered a fantastic volume and the singular weakness of the volume (being its peering sometimes too deeply into Luther’s psychology) does not mitigate the book’s worth. Even just a little.