Despite the severe economic retreat in 2008–2009, 401(k) accounts—because of their tax benefits—are still the best way for most people to investment for retirement. And, almost without exception, the books in the marketplace are pre–credit crunch, diminishing their relevance to consumers. Mary Rowland, a former personal finance columnist for The New York Times, breaks down how they work, why they are still a smart investment, how to keep an eye out for hidden fees, and why now is the time for investors of all ages to start reinvesting in their retirement.