NEW YORK (CNN/Money) - I've been looking for a good book that can explain the basics of investing. I came across your book, "Investing for the Financially Challenged," but I see it was published in 1999. Would you still recommend it given that the material may be dated, or would you recommend another book instead?

-- Anil Daswani, Sunnyvale, Calif.

I'm not answering this question because it gives me a chance to plug my book. (Oh, all right, maybe that accounts for a teensy weensy bit of my motivation, although I think only used copies are still available, so I don't get a dime in royalties.)

But in all honesty, I'm answering it more because it gives me a chance to talk about what I feel is one of the most important things someone must understand in order to become a savvy investor -- namely, the true principles of investing don't change from year to year or month to month or even day to day.

In my book -- and I don't claim to be the only financial writer who does this -- I lay out what I believe are some guiding principles that, if followed, can lead to investing success.

Spread your money among a broad range of asset classes -- large and small stocks, growth and value shares, large and small companies, different sectors of the market, taxable and tax-exempt bonds, governments and corporate.

Diversify by holding several securities within those asset classes -- not one growth or value stock, but several, not one bond with one maturity, but several with a range of maturities (if you invest in mutual funds, you automatically get this diversification).

Keep costs down -- every extra buck you pay in expenses is a buck that comes off your return. Keep trading to a minimum -- the more you trade, the more you generate transaction costs and, in taxable accounts, boost your tax bill (which reduces return. Frequent trading also increases the odds you'll make bad decisions.

Problem is, in the hurly burly of the market, investors often forget these principles -- or they get the impression that "the world has changed" and these principles don't matter anymore.

In the heady days of the late 1990s before the bubble burst, it wasn't uncommon to hear people dismiss diversification as a quaint outmoded concept. I remember having breakfast with one financial planner who referred to it as "di-worse-ification." His take was that spreading your money among many assets led to lower returns.

He's right in the sense that to the extent you spread your money among many assets, you won't have your money concentrated in the one asset that does the best in a given quarter or given year. What he forgot, though, was that it's virtually impossible to predict which classes will do best from year to year -- or even over longer periods.

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So while diversification does prevent you from hitting a home run in one investment, it also prevents you from striking out. It's a way of hedging your bets, reducing the risk that you'll guess wrong.

I bring this up because I've noticed both in the questions I get for this column as well as the questions I take on air each Monday from 4:40 pm to 5:00 pm on CNNfn's Money & Markets show that people too often approach investing as if the aim is to pick one or two investments that will outperform over the next quarter or the next year.

I'm often asked questions like, "Should I put my money in real estate or mutual funds?" Or, "I don't want to put my principal at risk -- what's a safe investment for my retirement money?" Or the recently popular, "Is now the time to get back into stocks or have I missed the boat?"

I'm not complaining about getting such questions. In fact, I'm happy people care enough to take the time to ask. But what these questions suggest to me is that people think of investing as "product" or "investment" centered, as if the challenge is to find the right vehicle at that point in time.

They should be thinking of investing as a process that starts with looking at your goals -- What am I investing this money for: college, retirement, a house down payment? And when will I need it? -- and then building a portfolio of complementary investments that will get you to that goal without taking too much risk.

And the funny thing is, the shape of that portfolio isn't going to change very dramatically whether you put it together today or tomorrow or 10 years from now.

Which brings me back to your question about investing books. My totally biased opinion is that the lessons I lay out in "Investing for the Financially Challenged" are as useful and valid today as the day the book hit bookstore shelves.

But there are plenty of other books I feel comfortable recommending, including John Bogle's "Common Sense on Mutual Funds: New Imperatives for the Intelligent Investor" and "The Four Pillars of Investing" by William Bernstein.

And I'll even recommend two books that were published long before mine: "The Intelligent Investor" by legendary value investor Benjamin Graham, which was originally published in 1949 but was re-released last year in a version containing updates and commentary by my MONEY Magazine colleague Jason Zweig) and "Extraordinary Popular Delusions and the Madness of Crowds" by Charles Mackay, which was published back in 1841, but in my mind still holds lessons that are applicable today about the various ways investors give in to investment hype and irrational exuberance.

So to sum up, you know the old adage about not judging a book by its cover? Well, when it comes to books that discuss the principles of investing at least, you shouldn't judge it by its pub date either.

Walter Updegrave is a senior editor at MONEY Magazine and is the author of "Investing for the Financially Challenged." He also answers viewers' questions on CNNfn's Money & Markets at 4:40 PM on Mondays.