'An Anonymous Girl' authors Sarah Pekkanen and Greer Hendricks

Sara sits down with the writers of the best-selling book.
5:09 | 01/24/19

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Transcript for 'An Anonymous Girl' authors Sarah Pekkanen and Greer Hendricks
Our next guests are the authors of "The wife between us," the book that took the country by storm in 2018. Now they're back with a brand-new story. It's the number one fiction book in the country. "An anonymous girl" welcome Sarah pekkanen and Greer Hendricks. Thank you. This is funny. We're being reunited. When I was on "The view" I used "The wife between us" as a book recommendation. As my favorite book. And you slipped me a copy of this new book. I did. You invited me down. I got to sit in the audience and watched you. And I handed you an early arc. If I knew that, I would have named it for that reason. One of the plot lines of the story is mismessaging a person in a text. Do you have personal experience with this? I think everyone has a personal experience of sending a wrong text and then going, oh, no, a second after you hit send. How much when you're writing comes from personal experience and people you know? I mean, really, not much, right? I mean, there was just one time. Thank god our life is not like this kind of crazy psychological thriller. But we were trying to come up with the name of a character. And I had a puppy named cooper who was always misbehaving, jumping on the furniture. I called out, no, cooper. And Sara said -- That's the name of our character. Dr. Thomas cooper is a character in the book. So there are personal touches if you look for them. Little details. Yeah. As co-authors, this is what throws me off. I wish I had a co-author in every college paper I wrote. How much do you have to write to be a co-? Is there a chance for me? And how do you guys even tag-team that? Do you hand off chapters or pages? Unlike most co-authors. They might alternate chapters or they each take characters. We decided we wanted to write every single line together. The question was, how are we going to do that? So my daughter, who was then 13, set us up with new fangled technology, Google docs and Google hangouts. That's how we write. I'm in New York, Sarah's in D.C. We're looking at the same screen. Talking every day from 9:00 to 4:00. I think even one person keeping track of some of those characters and story lines is confusing. Because part of the suspense is that it unfolds in a way that you would have to write it down somewhere. How do you keep track of where the story is going? When you're apart? One thing we do when we're together. We meet once a month. In a hotel room. All we do is work. That sounds scandalous. It does. And we work for 48 hours straight. And we bring giant post-it notes. We sketch out things to give us a global idea of the book. We'll write down character notes. Story arcs. We post them all over the walls. But one difference between us is that I like it really messy. Like Carrie Matheson. She call me Carrie. I seed weird patterns. I get ideas. This one is like, let's straighten it up. I can't work when the edges aren't all aligned. It's like a marriage of sorts. We're creative partners, professional partners, and bffs. Dr. Shield asks, would you ever read a spouse's or significant other's text messages. Ooh. Would you? No way. Bad karma. Not happening. Um, well, I mean, I know I'm on TV and I should say no. But -- I would say, I would never do it unless I had good reason to sneak a peek. One thing I also loved. I know you sold "The wife between us" to be turned into a movie. Yeah. And you also are selling this one. And writing it? Well, we're writing the screenplay for "The wife between us," which is thrilling. We're learning a new style of story telling. You had to Google how to write a screen play? How to pitch a screenplay. Thank goodness for Google. It's visual. It's dialogue. It's a great creative exercise and translate it for the screen. You write books I love. We already know that. I'm always looking for my next book. What's a book each of you have read lately that you would recommend? I read "Bad blood," the story of Elizabeth Holmes, who founded theranos. That, you know -- The big scandalous -- -- Pharmaceutical. Yeah. What we love is, we wish we had created Elizabeth Holmes. She's such a villain. That I wish we could have come up with her and created her for one of our books. What about you? "My sister is a serial killer." That say it -- says it all, right? I feel like I know that. Thank you for being here and sharing with us. I love the book. Love the book. "An anonymous girl" is available now. Don't go anywhere. We're going to be right back.

This transcript has been automatically generated and may not be 100% accurate.

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