In their first book together, Sisters First: Stories from Our Wild and Wonderful Life (Grand Central, Oct.), twin sisters and former first daughters Jenna Bush Hager and Barbara Bush write about their lives, including their White House years.

What made you decide at 35 to write a book together?

JH: This year, we realized more than ever that women really have to start having each other’s back, that women have to empower each other to do things that are outside their comfort zone and lift each other up. It’s not a typical political memoir by any means. It’s short stories of our life.

BB: In general, it has always been important for women to have each other’s back, and now there has been a much broader dialogue in the United States with people like Anne-Marie Slaughter and Sheryl Sandberg [discussing] more structural ways to support women.

JH: Also, I have two little girls now. And when they were born, I realized how lucky Barbara and I were to have each other.

What’s it been like to write together?

BB: Because we are twins, we do have such a shared experience. We were always in the same grade. We always had a partner on the first day of school. Even though we’ve lived very different lives and have different passions, our experiences have often been shared, which actually made it easier for us to come up with what we wanted to talk about.

What we wanted to show is both the extraordinary aspect of the life that we have been given in terms of the exposure that we have around the world [and] the really interesting people we’ve met, like the Dalai Lama or Vladimir Putin. But more of our life has been this very normal experience as sisters growing up and exploring the world in West Texas and then in Austin.

JH: It’s been really fun and slightly therapeutic to write it. People will come up to us a lot and say, How are you so normal? And it’s a very odd thing frankly to hear, because I think everybody prides themselves on being unique. We’re stereotyped into this caricature, into the president’s daughters, which in many ways we were. At the same time, we were 18 when my dad was elected. So we lived this life before then.

What books have influenced you on this project?

JH: Commonwealth by Ann Patchett, which I was reading when Barbara and I had the idea. It’s not a memoir, but it’s a fiction based on her life. I adore Jeannette Walls. And I also read Ariel Levy’s book recently, The Rules Do Not Apply. [Like our book] these books are not prescriptive.

BB: I think what’s been fun about this is we both are avid readers, and, obviously, our mother’s a librarian, so we grew up reading all the time. I reread Joan Didion’s The Year of Magical Thinking, and I loved Patty Smith’s memoir, Just Kids. I reread all of Americanah author Chimamanda Ngozi Adichie’s books, who has a TED Talk, “The Danger of the Single Story.” One of my favorite books is by Junot Díaz, a book of short stories, This Is How You Lose Her.

Today, 11 a.m.–noon. Jenna Bush Hager and Barbara Bush will sign Sisters First at the Hachette booth (2502, 2503).