"Dude, it was bad," said Behrendt, who's in Honolulu for a book-signing tomorrow at Borders at Ward Centre. "I confess everything in this book. If you thought I was some cocky dude who knows everything (from the first book), it's all broken down in this one.

"I was the guy she just wasn't into," he added.

Writing self-help books isn't exactly what Behrendt imagined he's be doing at age 41. He was thinking more along the lines of mega rock star.

"Yeah, and look at how that's going," he said, laughing.

But he's not complaining.

Behrendt went from stand-up comic to best-selling book author in less time than it takes a guy who's actually interested in calling you back. His first book, co-penned by fellow "Sex and the City" veteran Liz Tuccillo, is responsible for America's latest catch phrase, "He's Just Not That Into You" and remains on best sellers lists, having peaked at No. 1 worldwide. More than 2.5 million copies have been sold with translations into 16 languages.

There's more, too.

New Line Cinema purchased the film rights to the book — he and Tuccillo are working on a second draft of a screenplay — and he's got ideas for a talk show, radio show, sitcom and another stand-up tour.

In other words, he's into it. Deep.

"It's crazy," he said. "It's made my life really exciting and complicated ... Everything happened in a very strange way."

Like when someone from HBO approached Behrendt, then doing stand-up around L.A., to "tell us what it's like to be a man," he said. "It was great."

Behrendt spent three seasons as a consultant on the ground-breaking show, throwing in his in two cents — sometimes more — about manhood.

That's when the discussion happened.

Some of the female writers on the show started talking about men who seemed interested but never called back. Maybe he was scared. Maybe he was busy.

Maybe, Behrendt conjectured, he's just not that into you.

"I couldn't believe it," he said. "Here were all these bright women with amazing lives, pitching smart stuff, when that topic came up. I was like, 'Who are you now? Should you stay with him? Please.' "

His second book — a blend of straight talk, comedy and tough love — focuses on the breakup, something Behrendt and his wife, a self-described veteran of the dysfunctional breakup, have experienced firsthand.

In fact, their bad breakups practically led them to each other. He got sober after his split; she found strength after hers.

Then, as luck would have it, they were introduced by Behrendt's ex. They've been married for five years.

"I'm incredibly grateful (for my breakup)," said Behrendt, who has two daughters with Ruotola. "It really turned my life on its ear ... I learned how to take a (crappy) experience and make something revolutionary out of it."