Capital in the 21st Century, the new book about inequality by French economist Thomas Piketty, is generating excitement among progressives like few books I have ever seen in my lifetime. Take the video review I’ve posted above featuring MSNBC’s gloriously named Krystal Ball, for example. Ball calls Capital “mind-bending,” compares reading it to Neo’s awakening in The Matrix, and says after you’ve read it, you “can’t quite see the world in the same way.”

Ball’s intensity is goofy, but she’s hardly alone in her enthusiasm for the book. It’s a constant topic of conversation among progressive friends of mine. Most of the reviews, including my own, having been very strong. Paul Krugman’s review for the New York Review of Books hasn’t even been published yet, but he called Capital a “watershed” book in a recent column, and has also written a second column and at least two blog posts about it.

Sales of Capital appear to be brisk. I saw it rise as high as number 14 on the Amazon best-seller list (as I’m writing this, it’s at number 32). I wouldn’t be surprised if it made it on to other best-seller lists as well, and there will be undoubtedly be additional printings. Piketty himself is enjoying quasi-rock-star status. He will be appearing at a few public events later this month in the U.S.; some events in New York and Washington, DC have already sold out.

So how do we explain all this?

It’s certainly not because the book is a narrative-driven page-turner along the lines of Michael Lewis’s Flash Boys. Rather, it’s sober and scholarly. Yes, it’s lucid and readable — you don’t need math or an economics background to understand it. And Arthur Goldhammer’s translation is beautifully done. But it’s definitely a weighty, serious tome, not a pop book.

Capital is also decidedly not a feel-good book. The story it tells is a depressing one: that the natural tendency of capitalist societies is for wealth to become more concentrated and for societies to become more unequal. In the past, only very abnormal events like the Great Depression and wars have put the brakes on inequality. The course of action we could take that would be most likely to be effective in reversing inequality is a policy he also describes as “utopian.” Cheesy inspiration is not on the menu here.

So why are many progressives responding to this book so positively? There are a couple of reasons, I think. Most important is the timing. Economic inequality is a very disturbing phenomenon — so disturbing, in fact, that people’s tendency is to deny it. Studies have shown that Americans dramatically underestimate the degree of economic inequality in our society. There’s plenty of blame to go around for that: towards Republicans for shamelessly lying to the public about inequality, and Democrats and the media for largely avoiding the subject until recently.

But levels of inequality in our society have been spiraling out of control, to the point where the problem can no longer be ignored. Occupy, with its language of the 99 percent vs. the 1 percent, brought the issue out of the shadows and supplied a language with which to discuss it. Also, we’ve had five years of a Democratic president, but the problem has still not improved. Many people are frustrated and are looking for a deeper, more satisfying analysis and solutions. Piketty’s book provides them.

I also think people are responding to the book’s bigness, boldness, and ambition. Progressives in this country have only recently emerged out of a political era where the idea of an exciting liberal policy initiative was midnight basketball. During the last decade — a period when this country grappled not only with soaring economic inequality but with climate change and wars of choice we waged on two fronts — the best-selling, most acclaimed economics book of its time brought all of econ’s most up-to-date, high-tech wizardry to bear on such world-historic problems as cheating sumo wrestlers.

It’s a bloody relief to read an economist who possesses the honesty and seriousness to dispense with the petty, frivolous crap and dive in to something real and profoundly important.

There’s real power in Piketty’s analysis, too. I used to be, like most American progressives, optimistic about where politics were headed during my lifetime. The arc of the universe bends towards justice, right? I sincerely believed in the myth of progress. Things would get better. That bad economic path we got started on in the 70s? That continued into the 80s? And the 90s? And the 00s? And now is continuing well into the 10s? That’s just a short-term deviation, we’ll soon set things right as rain! Then economic inequality will decrease, economic growth will return, and all will be well.

That was a nice dream, but I don’t really believe it anymore. It’s not that I’m pessimistic, exactly, but I’ve become much more agnostic about political progress. Piketty’s analysis as to what happened to the economy, and where it is going, is powerful and persuasive. Krystal Ball may sound loopy, but she’s right: this book really does make you see things in a new way. This is a book that destroys the comfortable, largely unconscious assumption many of us had that the natural tendency of modern economies was toward more equality. The truth is actually the opposite.

Piketty’s argument about why inequality will continue to spiral depends in large part upon his analysis that holds that r, the return on capital, will exceed g, the growth rate. The future, of course, is notoriously difficult to predict. Perhaps Piketty is wrong and growth will return to its previous levels.

But even economists as conventional as Larry Summers are cautioning that we may face years of depression-like “secular stagnation,” absent aggressive government intervention in the economy. Given such portents, I think we have to take Piketty’s warning of a dystopian inegalitarian spiral very, very seriously.

I doubt many of us who have responded to Piketty’s message would have done so had it not been for the shock of the brutal economy of the past half-dozen or so years. The timing was crucial. The book is an important step in what’s been a long, slow reckoning with a painful truth. Growing inequality appears to be the natural order of things in a capitalist society, absent certain rarely occurring catastrophes. If we want to put the brakes on that, we will have to take some fairly dramatic actions — such as steep increases in the marginal income tax rate on top incomes and the imposition of a wealth tax, to name two of the most important policies.

A generation of women responded powerfully to Betty Friedan’s feminist classic The Feminine Mystique because it identified “the problem that has no name.” Today’s progressives are responding so intensely to Piketty because, like Friedan, he brings great moral urgency to bear on a problem that infects every aspect of human life and human society, but that few other contemporary observers had seen with such clarity.

Enacting the sweeping changes that are required to deal with the problem will be extremely difficult. But at least we have a much clearer, unvarnished view of what we’re up against. That in itself is a kind of liberation, and the excitement it generates may explain progressives’ ardent enthusiasm for this book.