Greg Behrendt's bestselling dating book -- now a film -- began as a blunt, straightforward comment to a woman who wondered why a guy she was interested in, didn't want to sleep with her.

The comedian was working on the hit television show "Sex and the City" at the time, and in the typical pull-no-punches style that came to characterize the book, he told his coworker "he's just not that into you."

The line would become the name of the book that followed -- a guide to help women spot when a man has lost interest and how to deal with it proactively -- and now the film.

"That sentence has turned into this phenomenon, and it's been like a gift bag for me," Behrendt told CTV's Canada AM on Wednesday.

He joked that the film, a romantic comedy, is helping some unknown actors get their start.

"They've given a couple of independent film actors a chance to shine. I don't know if you've heard of some of the names, Jennifer Aniston, Scarlett Johannson, and Ben Affleck getting his start in this movie."

The film version of "He's Just Not That Into You" also stars Jennifer Connelly, Kris Kristofferson and Drew Barrymore and was written by the same team that did "Never Been Kissed."

Behrendt himself even makes a cameo on the film.

Though the book, published in 2005, was a success, Behrendt said he was surprised when he was approached about turning it into a film.

"It's a self-help book. There's no plot," he said.

"There's the basic stuff that's in there that's if you're dating a guy that's married maybe you should find someone that isn't married -- one of the simple rules. The fact that it's turned into this film is exciting, man. It's just -- it's become sort of a cultural phenomenon."

After the success of the first book, Behrendt kept up with the dating advice theme. He wrote a second best-seller, "It's Called a Break-up Because It's Broken," and is now working on a third called "It's Just a Bleeping Book."

He said it all started with that one straightforward comment, and the realization that sometimes people just need to be told the truth, even when it hurts.

"We're really lucky because we did that thing which has never been done. It's basically a book I wrote to my sister stop dating that jerk you've been going out with that cheats on you," he said.

Behrendt is in Canada touring with the Just for Laughs Lipton Comedy Tour.