John C. Bogle's The Little Book of Index Investing is a power-packed explanation of why outperforming the market is an investor illusion. Instead, the founder of The Vanguard Group—the man who's been called 'the conscience of the investment industry'*—recommends a simple, time-tested investment strategy that can deliver the greatest return to the greatest number of investors: indexing. Why? Investing is a zero-sum game where transaction costs, taxes, poor investment diversification, and poor market-timing (an affliction for most investors) hurts your portfolio more than it helps. Indexing eliminates that hurt. Bottom-line, if you can't be an index, why not invest in one? And you'll be all the happier and richer for it.
*Time Magazine