Oprah Winfrey has picked Isabel Wilkerson’s Caste: The Origins of Our Discontents as the latest selection for her popular book club, CBS News reports.

Wilkerson’s book, about the complex history of race and social divisions in the U.S., drawing comparisons with the caste systems in India and Nazi Germany, is one of the most anticipated books of the year. It’s also one of the best reviewed ones—a critic for Kirkus called it “memorable” and “provocative,” while Dwight Garner of the New York Times declared it “an instant American classic and almost certainly the keynote nonfiction book of the American century thus far.”

On CBS This Morning, Winfrey said Wilkerson’s book is “the most necessary for all humanity book that I have ever chosen.”

“Usually, I’ve called authors over the years and said, ‘I’m going to choose your book,’” Winfrey said. “And sometimes authors cry and they’re excited. It’s the first time I called an author and I was crying. I was crying because I’m so moved by this book.”

“This is not a book that I wanted to write,” Wilkerson said. “This is a book that compelled me, that called to me, that I felt I had no choice but to write it.…We have actually made so much progress when it comes to things that we consider to be traditional, old-school racism of the Klansmen of the late 19th century and early 20th century.…And so now we are in a very different place.”

Wilkerson’s previous book, The Warmth of Other Suns, won a National Book Critics Circle Award in 2011.

Winfrey’s imprimatur has already affected the book’s sales—as of Tuesday morning, the book had skyrocketed to No. 6 on Amazon’s bestselling books chart.

Michael Schaub is a Texas-based journalist and regular contributor to NPR.