Q: The Only Investment Guide You'll Ever Need (Harcourt, 2005) has been in print and revised since 1978, and since then, it's reached more than a million readers. What have you updated for this edition?
A: Everything. The basic advice never changes, but the Internet addresses sure do! And the tax laws. And I've added a section to try to help you deal with your aging parents or grandparents, and another on timber (who says money doesn't grow on trees?). And I make this really impassioned pitch for getting your bride-to-be a really nice synthetic diamond ring—and a $4,000 Roth IRA with the saving—because the ring is indistinguishable from a real one, and one Roth IRA contribution could be worth a quarter million tax-free dollars when the two of you are celebrating your diamond anniversary.

Q: Who can benefit the most from this book?
A: Me. It's been really great for me, although by now—knock wood—I am able to give the royalties to charity. But beyond that, I like to think the book has broad application. Especially if someone is just starting out in some way…graduating and embarking on a career, marrying and starting to plan a family, even, sadly, divorcing and having to cope on one's own or losing a parent and inheriting a chunk of money for the first time.

Q: The market is flooded with investment guides—some with sensible advice and others with get-rich-quick promises—why should readers choose The Only Investment Guide You'll Ever Need?
A: I hope it's fun to read, and I hope it will save them at least $1,000 a year just on the smart-spending tips. I hope it will help motivate readers (or their spouses) to want to save that money, by helping them see the big picture and the value in taking control of their finances. I hope it will make them a lot more confident about money—and a lot less susceptible to foolish mistakes that could part them from it. One of the advantages of the book's having been out there for more than a quarter century is that there's been time for people to report back on what it's done for them. The letters and e-mails over the years have made my mother very happy.

Q: The New York Times calls you a "master when it comes to entertaining while educating" and says your "advice has remained consistent over the last quarter-century, and that is the way it should be." What would you like readers to gain from your book?
A: Confidence, financial security, a common-sense framework within which to make financial decisions, and an amused little crinkle around their eyes as they read it.

Q: With advice and tips ranging from the cheapest way to rent movies and yearly expenses to understanding the stock market and financial planning, how do you stay current on the vast range of topics covered in each chapter?
A: Google. And a constant flow of suggestions from the readers of my Web site.

Q: In your experience, what's the most common mistake people when investing?
A: They have no overall plan, and, worse, tend to buy the things that are in fashion (i.e., when they're expensive, not when they're cheap) and the things salesmen are paid to sell them rather than things that represent the best value.

Q: You're Harvard-educated—for both undergraduate and graduate studies—and since the age of twenty-three, you've contributed to New York magazine, Esquire, Time, The New York Times Sunday Magazine, Money, and Worth, among others. You've appeared on several television shows, including Today, Good Morning America, and Face the Nation, and you cohosted Beyond Wall Street with Jane Bryant Quinn on PBS. On top of all of that, you've published more than ten books, and you're currently the treasurer for the Democratic Party. What lies ahead in your future?
A: You're making me feel very old.