Hillary Clinton said Thursday that the act of writing her book is sometimes "exhausting" and requires her to either talk a walk, or take a nap.

"Sometimes I'll work on it for a couple of hours. I have a little writing area in the attic of our little farm house," she said at the Book Expo in New York.

"And you know, I'll work on it, and I've got, you know, great colleagues who are doing research and helping me think through how best to present things," she said.

"And it's so exhausting that I just literally have to get up," Clinton added. "Either go for a walk or go to bed. Those are my two choices."

Clinton said her book would be about her failed presidential election and how she felt about it as it unfolded in full public view last year.

She said she was writing about her experience as the first woman to ever be nominated as a major party candidate.

Clinton's memoir is expected to be published in September.