This slim volume, skinnier than a size-zero model, belongs to the increasingly tiresome genre of clever-dick lit. If you have heard of Blink, Nudge, Snark or Freakonomics, you’ll know the form; indeed you could probably write one yourself. Choose a proverb, any old proverb: ‘more haste, less speed’, say. Reformulate it as a cute title – Trudge: What the Tortoise Can Teach Us About Wealth, Health and Happiness – and the book more or less writes itself. Sit back and wait for Barack Obama or David Cameron to be seen reading it. You are now officially a guru.

Even so, you may struggle to keep pace with Cass Sunstein, whose Nudge was admired by both Obama and Cameron. He is the Felix Frankfurter Professor of Law at Harvard, the Harry Kalven Visiting Professor at Chicago, the author or co-author of thirty-five books and now also a