"Brettschneider's book, addressed to a presidential aspirant, begins with the question 'What do you need to know to be president?' The answer: 'Most of all, you need to know the U.S. Constitution.' This framing is one of the book's great virtues: It moves the focus away from the too-common and too-narrow question of what the courts might force a president to do in the name of the Constitution to the more capacious question of how a president herself should understand her constitutional role."