Move over, "Fifty Shades of Grey." Instead of romance, a book by French economist Thomas Piketty on income inequality and capitalism is the No. 1 best-selling book on Amazon.com.
Piketty's "Capitalism in the Twenty-First Century" is generating so much interest among economists and policy makers that it's temporarily out of stock on Amazon.
At nearly 700 pages, it's not a book for beach reading by casual readers -- unless a mix of dense economic data and history is your thing.
Piketty examined decades of historical data from 20 countries to compare income inequality over time and concluded that the U.S. economy has seen the wealth of the 1% grow to dizzying new heights. Wealth isn't trickling down as some argue, Piketty said. Moreover, he warns that rising inequality will undermine democracy and generate discontent.
Though income inequality is a hot-button issue, it's not often an economics book tops a best-seller list.
"It's un...believable. It's astonishing that an economics book would be this high on any mass market book list," said David Shulman, a UCLA Anderson Forecast senior economist. "It's going to put you to sleep. This book is dense reading."
Shulman, who reviewed the book in a blog post, said that despite its length, "Piketty has written a book that is and will continue to be much discussed. It should be the subject of serious debate and readers should note that the book is not an all-encompassing treatment of inequality.
He has "struck a real chord," Shulman said. Income inequality "is a very topical issue in the country."
The book, he said, has highlighted the ideological divide that is likely to stir strong opinions from liberals (who praise the work) and conservatives (who are criticizing Piketty).
Paul Krugman, in a review for The New York Review of Books, said Piketty "has written a truly superb book." Over at the conservative National Review, James Pethokoukis criticizes the book as a reincarnation of Karl Marx's "Das Kapital" and said Americans are more wealthy today than they were in the 1920s.