John Bogle, the founder of Vanguard and creator of the first index mutual fund available to retail investors, makes the definitive case for passive investing with characteristic precision and moral clarity. The core argument is mathematical and difficult to refute: because the total returns of all investors in aggregate must equal the market return minus costs, the average actively managed fund must underperform a low-cost index fund by exactly the amount of its expenses. Over decades, this cost drag compounds into a devastating gap in outcomes. Bogle supports this argument with rigorous historical data showing that the overwhelming majority of actively managed funds fail to match their benchmark index over any extended period, and that picking the rare outperformer in advance is essentially impossible. The book explains how fees, turnover costs, tax inefficiency, and the temptation to chase recent performance all conspire to erode investor returns. Bogle also covers bonds, balanced funds, and retirement planning, all through the lens of cost minimization and long-term discipline. Written in plain language with a passion for investor advocacy, this is the essential text for anyone considering the choice between active and passive investment strategies.