The Index Card by Helaine Olen and Harold Pollack is a personal finance book that distills essential money management advice into ten simple rules, which originally fit on a single index card. It argues that complicated financial strategies are unnecessary and that following a few core principles, like saving 10-20% of income and avoiding credit card debt, can lead to financial success. The book provides an easy-to-follow, step-by-step guide to financial security and is suitable for beginners and experienced individuals alike.