Great political leaders, with a tiny number of exceptions, are complicated people who possess both appalling flaws and magnificent virtues. Oliver Cromwell was not one of those exceptions. He sought and relished the demise of political enemies, hogged glory for military feats rightly belonging to others, perpetrated wartime atrocities, and equated God’s will with his own intentions. But he also undermined a class system that elevated birth over ability, dealt a death blow to the divine-right monarchy, and forced the English nation to reckon with the reality of religious—and, by extension, political—diversity. “He was,” Ronald Hutton writes in “The Making of Oliver Cromwell,” “courageous, devout, resolute, principled, intelligent, eloquent, able, adaptable and dedicated, but also self-seeking, unscrupulous, dishonest, manipulative, vindictive and bloodthirsty: definitely not somebody to be taken simply at his word.”