The Little Book of Common Sense Investing, written by John C. Bogle, is a guide to passive investing and index funds. Bogle, the founder of Vanguard Group, advocates for a simple and low-cost approach to investing. The book explains the benefits of index funds and highlights the pitfalls of active investing. It emphasizes the importance of diversification, long-term thinking, and keeping investment costs low. The Little Book of Common Sense Investing is a valuable resource for investors looking to build a solid investment portfolio without the complexities of active trading.