Before Charles and Diana, before the impeachment of Bill Clinton, and long before the slogan "the personal is political," an astonishing British royal sex scandal threatened to trigger a revolution. Its lessons for leadership, popularity, and the impact of the absurd on history are fascinating.

In The Trial of Queen Caroline, Jane Robins tells the story of one of history's least happy marriages. The future George IV could not be bothered to meet Caroline, Princess of Brunswick, a woman "with indelicate manners...and not very inviting appearance," before she arrived for the...