Economics is the rigorous working out of the principle that people respond to incentives. In Discover Your Inner Economist, Tyler Cowen offers Smart Shopping for Metrofexuals, although his subtitle is Use Incentives to Fall in Love, Survive Your Next Meeting, and Motivate Your Dentist. He offers three screens for identifying good economics: can the idea be summarized on a "moderate-sized postcard" (I vote for the 4x6); can the researcher summarize the argument in a way his or her grandmother will grasp it (I believe that's Paul Samuelson's mother-in-law principle); and does the idea cast an odd phenomenon in a new but now self-evident framework, which he calls "the Aha! principle." So far, so standard: there are plenty of other economics books that do this sort of intellectual puzzle solving, and there is disagreement among practitioners about the usefulness of the work, whether in making the field accessible to curious outsiders, or more fun for students, or for developing a research agenda. The cases in Discover Your Inner Economist are more obscure than those in The Economic Naturalist (reviewed here) or The Logic of Life (reviewed here) or The Undercover Economist (reviewed here) or Freakonomics(reviewed here). Perhaps the short form of Book Review No. 47 is Diminishing Returns to Partial-Equilibrium Anomalies.