The owner of a housewares store recently confessed to me that her top-selling item is a plastic disc used to drain cans of tuna.

This disc is not a necessity in every kitchen. But it is colorful and cheap: $3.50.

We all love bargains. We all distrust bargains, and revile what's cheap. Author Ellen Ruppel Shell tries to get to the bottom of this contradiction in her fascinating account of how we came to be this way, and what it costs us in the long run.

It is, at bottom, a disturbing book in which we see reflections of ourselves: ignorant of how prices are set, unsure what constitutes a deal, chumps for anything selling cheap, and puppets of the Wizards of Marketing.

Shell introduces us to a few of these guys who have persuaded us that rock-bottom prices will reward us with a better life, especially if we buy lots more than we need. "Their goal," she writes, "is to distract customers from thinking hard about a purchase or, for that matter, thinking hard about anything at all."

The ancient marketplace, she tells us, "was built on a balance of power between buyer and seller. ... Overcharge a man for your lamb, and he's sure to overcharge you for his pots or give you a bad haircut when you patronize his barbershop."

Now, we not only don't know the people we buy our beef from, but we don't know who produces the beef, or where. We can't imagine the faces of the women who sew our $8.99 shirts, or the people who press the wood chips that become the boards of the $29.99 bookcase we buy from Ikea -- a design-on-a-discount enterprise that takes quite a lashing from Shell.

And our hearts no longer beat fast at a well-crafted hand-made sweater that might last a lifetime so much as at one whose price has been cut in half at Wal-Mart. That Wal-Mart sweater is like so much of what the author herself admits to having bought, cheap stuff that ends up in the back of a closet, "a bargain-hunter's pile of shame."

What fun we had! But we hate ourselves in the morning. And the tracks of our cheapskate tears ultimately stain the faces of Third World workers whose wages, shaved by multinational competitors, are forcing down our own.

This book is not bedtime reading. It demands focus and attention -- it has 40 pages of footnotes! -- and may call into question every purchasing decision you've ever made. Your mattress, for one. Stores, she writes, "typically rotate discount offers through a number of mattress brands. ... In reality, no mattress is significantly discounted; rather, the brands not on sale carry inflated prices."

You may also lie awake wondering what to do tomorrow. Shell gives scant space to solutions, other than coaching us to study products and vote for quality over price. But what of those who can't afford to buy anything but the cheapest shoes and the cheapest oranges? How do you "study up" on mattress quality? Where do you find sweaters made in the USA at reasonable prices?

Maybe she's saving that for her sequel. I'd buy it, even at full price.

Susan Ager, a former Detroit Free Press columnist, can be reached at susan@susanager.com