Luther as skeptic
Martin Luther: The Christian Between God and Death, by Richard Marius
Most of Martin Luther's biographers end their books in the 1520s, some 20 years before Luther's death. This allows them to leave Luther as a revolutionary (and theological) hero, rather than as an establishment curmudgeon. And it enables them to avoid dealing with the older Luther's repugnant attacks on Catholics, Jews, Turks and fellow Protestants.