We return to Andrew and Briony. There is a bit in chapter three in which Andrew is describing to his therapist a road trip: our two young lovers drive from southern California to New York City, taking turns at the wheel. For the final stretch, beginning in Atlanta, the one not at the wheel was reading out loud. From Mark Twain, whom Andrew refers to, familiarly as MT. The book of MT's that enlivened those hours and days of driving? The therapist guesses Huckleberry Finn. Andrew corrects him. The book was The Prince and the Pauper. And he puts what I take it is a Doctorow-esque gloss on this book: The two boys exchange identities, the prince is the pauper and the pauper is the prince. Briony liked the romance of that, Clemens saying there's nothing to royalty but the assumption. But it's more than a democratic parable: it's a tale for brain scientists. Given the inspiration, anyone can step into an identity because the brain is deft, it c...