If the historian Joseph J. Ellis has a project — an unfairly pedestrian term to describe his rich body of work — it is to restore to the nation's founders some measure of their humanity. In books like “Founding Brothers,” which won the Pulitzer Prize in 2001, and “American Sphinx,” a brilliantly drawn portrait of Jefferson, Ellis renders the founders in fine shadings: wise and bold and prescient, yes, but also, at times, blinkered and uncertain, men in conflict with one another and even themselves.