The premise of this book originated when University of Chicago professor Harold Pollack, in the middle of a podcast interview, jotted down everything he believed you needed to know about personal finance on a single index card and shared it online — and the image promptly went viral. The book expands the nine rules on that card into a fully developed personal finance guide, with financial journalist Helaine Olen co-authoring the historical and critical context that explains why simple, obvious financial principles are so rarely followed in practice. The nine rules cover the essential bases: max out tax-advantaged retirement accounts, buy inexpensive index funds, avoid actively managed funds, pay off credit card debt in full, invest no more than ten percent of a portfolio in individual stocks, take the free money of employer 401(k) matches, buy adequate insurance, make a will, and be skeptical of financial advice that enriches the advisor. Olen contributes sharp analysis of the financial industry's systematic effort to convince ordinary people that personal finance is too complex to manage without professional guidance — guidance that frequently serves the advisor's interests more than the client's. Together, the authors make a compelling case that the complexity of modern financial products is largely manufactured to generate fees, and that the core decisions required for financial security are genuinely achievable by anyone willing to follow a few consistent principles.