In 1993, Peter D. Kramer wrote "Listening to Prozac," a book that explored the ethics of prescribing what was then a relatively new class of antidepressants that, quite separate from treating depression, made patients more confident, outgoing and energetic - in short, "better than well."

The book was a best-seller, Kramer became a public figure and the medication, selective serotonin reuptake inhibitors, was widely prescribed.

But the phenomenal success of the drugs, and a cultural bias in favor of psychotherapy - a sense that self-understanding is better than popping a pill - led to a backlash against psychopharmacology and a spate of articles questioning their effectiveness. Was it possible the reprieve that patients reported was due to the placebo effect?

Now, after pursuing other interests, Kramer has rejoined the debate with a new book, "Ordinarily Well," that offers a carefully argued and convincing case that antidepressants not only work but also are an essential tool in the treatment of depression. The title is medical lingo, another way of saying the drugs are "as beneficial as most treatments that doctors are content to use."

Kramer begins by reviewing the development of pharmaceuticals to treat depression, from tricyclics and MAOIs in the 1950s to SSRIs in the '80s, the category that includes Prozac, Zoloft and others. He evaluates major studies of the drugs; these are fairly technical chapters requiring close attention.

Throughout the book he weaves in stories from clinical practice about people whose lives markedly improved on the drugs. He also addresses their downside, including potentially worrisome side effects and the fact that they don't always work.

After laying out the pros and cons, and clarifying the murky debate about efficacy, he remains a believer. The deniers, he says, don't recognize the "scourge" of depression for what it is: "a progressive, destructive multisystem disorder fully worthy of medical attention."

So, if you buy his premise, why do antidepressants work?

"The prevailing understanding is ... that the medications restore resilience in the mind and brain, allowing the growth of new nerve cells and the elaboration of new connections between cells. The drugs 'permit' depression to diminish by allowing repair and new learning to proceed in brains and persons previously left 'stuck' in depression."

Anybody who wants to hear what Prozac has to say will be interested in this book.