Oprah Winfrey's Book Of Columns, What I Know For Sure

Oprah Winfrey's latest book project is a collection of magazine columns by a writer she knows quite well.

"What I Know for Sure" features the monthly essays that Winfrey has written for O, the Oprah Magazine over the past 14 years. Flatiron Books, a new nonfiction imprint of Macmillan, announced Wednesday that "What I Know for Sure" will come out Sept. 2. It will be the imprint's first release.

According to Flatiron, the book will be organized around such themes as joy, gratitude and possibility. Winfrey has said she named her column "What I Know for Sure" after film critic Gene Siskel asked her "What do you know for sure?" during an interview. She has called the columns a way of "taking stock" of her life.

Winfrey will write the book's introduction