Roosevelt seeks to prove that Cromwell's rise to power was the first modern struggle for religious, political, and social freedom. First, Roosevelt explores the actions of the Stuart kings and how those actions became more and more tyrannical and incompetent. Next, Roosevelt examines the Long Parliament and how Charles I's despotism forced the Members of Parliament to revolt. Roosevelt then studies how Cromwell came to the decision to have Charles executed after the second Civil War. Finally, the author looks at Cromwell's performance as a soldier and leader in the Scotch and Irish campaigns, particularly how he dealt with religious differences in his army. Roosevelt clearly supports Cromwell's actions up to the point of the Commonwealth. But Roosevelt makes his reservations with Cromwell's actions as Lord Protector clear: while Cromwell had good intentions, his manner of enforcing them and his unwillingness to compromise in politics were the causes behind the failure of greater religious, political, and social freedom in England.
Roosevelt writes with a passion and wit unseen in many current histories. As a non-professional historian, he is unrestrained by notions of objectivity, and he heaps scorn and insults upon the Stuart kings in a comical manner. Roosevelt obviously admires Cromwell, finding an excuse for almost all of Cromwell's actions, with the exception of Cromwell's actions as Lord Protector. That Roosevelt writes for an American audience is shown by his frequent mention of the American Revolution and Civil War as examples and comparisons. He contrasts Cromwell with Washington several times, although Cromwell did not quite match the character and abilities of Washington. Roosevelt's style is sometimes complicated, but his enthusiasm for his subject and his frequent forays into name-calling make for a highly entertaining biography. There are no citations of any kind, but there is an extremely detailed index.