There are actually two authors credited with writing the book, He just not that into you: the no-excuses truth to understanding guys, and they are Greg Berhrendt and Liz Tuccillo.
The book He's just not that into you was written by Greg Behrendt and Liz Tuccillo. The movie is based on the book and was written by a team that included Greg Behrendt and Liz Tuccillo as well as Abby Kohn and Marc Silverstein. The movie was relased in 2009 and the book was published in 2004.
The authors of this book are Greg Behrendt and Liz Tuccillo who present the ways to tell when a relationship may not be worthwhile and what to do about it.
The book in question was written by Greg Behrendt. He also wrote "It's Called Breakup Becase It's Broken" and also has two DVDS called "Green Behrendt is Uncool", and "Greg Behrendt Is That Guy from that Thing."
