RENEE MONTAGNE, HOST:
The hot book out right now is called "Capital in the Twenty-First." It's a rather wonky tome about inequality by French economist Thomas Piketty. He's been selling out events on his U.S. tour.
NPR's Kelly McEvers went to find just why his 700-page book is so popular.
KELLY MCEVERS, BYLINE: The book has spent 43 days as Amazon's number one bestseller. Amazon has run out of hard copies and is now selling digital versions of the book for 22 bucks.
Whether people have finished the book or not, "Capital in the Twenty-Century" is being talked about and debated across the country - at think tanks, on editorial pages, and at universities.
Piketty's most recent appearance was at the University of California, Berkeley, a place where he was pretty likely to find fans like seniors Christopher Hussy and Naomi Egel.
NAOMI EGEL: I had two classes this semester where professors keep bringing him up. I figured if he's coming here it's a pretty cool opportunity.
MCEVERS: Have you read it?
EGEL: I have not read it, it's for when finals are over.
MCEVERS: Oh yeah totally, 'cause it's 700 pages.
CHRISTOPHER HUSSY: This summer, this summer.
MCEVERS: Public policy grad student Kevin McNellis hasn't read the book yet, either. Still, he says the conversation about inequality is not just one for the ivory tower.
KEVIN MCNELLIS: I was just at Easter with some family and they could not care less about politics but, you know, there was this general sense that, you know, the game is rigged and it's harder to find good-paying jobs and they're like this wasn't how it was when we were kids.
MCEVERS: So what does a French economist have to say about a system some Americans think is rigged?
UNIDENTIFIED WOMAN: If we do not clear the walkways, this event will be shut down.
MCEVERS: Well first, he draws so many people the fire marshal shows up. And then Thomas Piketty or Thomas Piketty, if you say it the right way, explains his 15 years of research, combing through tax records that span centuries.
THOMAS PIKETTY: This is the largest historical database on income and wealth distribution available. But...
MCEVERS: Piketty has found that over time, the rising tide has not lifted all boats. Rather, save for a few decades last century, wealth is fast accumulating in one small place - at the top. In 2012, 50 percent of the wealth was held by the top 10 percent of the people.
PIKETTY: You have to ask yourself, where is it going to go? Is it gonna? Is it going to go to 60 percent 20 years from now, 70 percent?
MCEVERS: So to slow this accumulation, Piketty proposes a progressive tax on net wealth. Basically, the bottom 90 percent would pay less tax, and the top 10 percent would pay more, needless to say, it's an idea that already has critics.
Still, after the lecture and the Q and A, Piketty said he's surprised by how popular he and his book are.
PIKETTY: Well, I mean this is certainly, you know, the maximum I could expect.
MCEVERS: But he says maybe it makes sense for him to tell America's story. After all, he says, the U.S. invented the progressive tax in 1919, when class-based Europe was reluctant to do the same.
PIKETTY: You know, sometimes it's easier to, you know, for outsiders to remind you about your own history.
MCEVERS: After getting his book signed, Piketty fan Phillip Hoon says he's in the top 10 percent. That's why he came to see Piketty.
PHILLIP HOON: The way he's presented it, there are risks that affect me and my family.
MCEVERS: Like what? Being taxed?
HOON: But the flip side, I've got children who aren't earning incomes and then I've got other family members who're barely making livings on subsidies and stuff like that. And so if you could find some mechanism to make things better for them, that's why it's really key to have this brought to people's attention.
MCEVERS: When pollsters ask Americans about inequality, they by and large agree it exists. That's different from other big issues like climate change.
The problem, says Carroll Doherty of the Pew Research Center, is when you start to drill down on inequality.
CARROLL DOHERTY: We asked people, Okay the gap is increasing, you say the gap is increasing, and there seems to be pretty broad agreement about that. Why? And there's really no great consensus among the public about why this is occurring. I think that multiple reasons were given.
MCEVERS: Doherty says there's also disagreement over what to do about inequality. Republicans, of course, favor less government - Democrats more. Doherty found more people think government should intervene if you ask about something concrete, like poverty.
The definition of inequality and whether Piketty's way of fixing it will work, that's something even people at Berkeley can't agree on.
Kelly McEvers, NPR News. Transcript provided by NPR, Copyright NPR.