Why write (or read) another book about models of banking? It sometimes seems that banking is passé — that the real financial action lies elsewhere. A recent survey (R. Greenwood and D. Scharfstein, “The Growth of Finance,” J. of Econ. Perspectives, 2013) documents the explosive growth in non-bank financial products and services. Securities markets more than quadrupled in size, from 0.4 to 1.7 percent of GDP between 1980 and 2007, on the eve of the crisis. Surely this is where we should focus — the busy secondary markets for bonds, equities, securitized products, and over-the-counter derivatives. Yet, reports of the demise of traditional banking have been greatly exaggerated. Credit intermediation, which includes traditional deposit-taking and lending alongside banks’ transactional services such as credit-card accounts and ATM activity, have also grown. Starting from a much larger share, Greenwood and Scharfstein (2013) calculate that credit intermediation grew from 2.6 to 3.4 percent of GDP over the 1980–2007 period. When the dust has settled on a quarter century of remarkable growth, banking is still roughly twice the size of securities markets.