If you've ever wondered why he didn't call after your great first date or why he's not ready for commitment, the answer is simple - he's just not that into you. Women's Editor Linsay Jennings looks at a self-help book which has topped the American bestseller lists, and has now hit British bookshops.

I ONCE went out with a guy who was incapable of phoning when he said he would. If we went out on a Saturday night, you could guarantee he would phone at least three days after he had promised - turning any post-date glow into an over-analysed mess. If he had failed to call at all, I could have moved on and dumped him. But, spurred on by many alcohol-fuelled chats with my friends, we decided that it was just part of his laid-back nature.

If only I'd had a copy of Greg Behrendt and Liz Tuccillo's book, he's just not that into you, I would have known the reason for his tardiness.

The idea for the book came from a script-writing session for the hit television show on love and dating - Sex and the City. Fans will recall the episode when Carrie's boyfriend Berger, explains to Miranda why a man declined to go back to her apartment after their first date - because he just wasn't that into her.

The predominantly female writing team of SATC were talking about the men they were seeing when one of them decided to consult the only man in the room. She told Greg that she had been dating a guy and that they had been to a movie and he had kissed her afterwards. But she said that he had declined to come up for coffee because he had a really important meeting in the morning.

Continues Greg: "So I asked if she had heard from him. "Well that's the thing," she said. "This was like a week ago and then today he emails me and is like "why haven't I heard from you?"

"Here was this beautiful, talented, super-smart girl who was a writer on an award-winning TV show, a show known for its incisive observations about men, who you would think could have her pick of any dude around. This superstar woman was confused about a situation which to me was so clear. Actually, "confused" was the wrong word, because she was too smart for that. She was hopeful, not confused, but the situation was hopeless, so I broke the news to her: "He's just not that into you."

Co-author Liz Tuccillo says the women were "shocked, amused, horrified and above all intrigued" by the straight-talking Greg.

"We sensed immediately that this man might be telling the truth," she says, "a truth that we, in our combined hundred years of dating experience had never considered and definitely never considered saying out loud.

"We had excuses for all these men - from broken dialling fingers to difficult childhoods. In the end, they were shot down by Greg's powerful silver bullet."

According to Greg, if a guy is into you, he will let you know it. He will call, he will show up on time and he will want to meet your friends. He'll go out for Sunday lunch with you and your parents and he will want to go on that romantic mini-break. And the reason he doesn't call is simple.

"We would rather lose an arm out of a city bus window than tell you that you're not the one," he says. "We are quite sure you will kill us or yourself or both - or even worse cry and yell at us. We are pathetic, but the fact remains, even though we may not be saying it, we are absolutely showing you all the time."

But I believe this "silver bullet" works both ways. I can remember going out with a hairdresser who promised so much with his gorgeous looks and great body, but turned out to be Mr Monosyllabic when he was sober. When it came to dumping him, I chickened out and came up with a range of excuses from being ill to having to work overtime. Eventually, overcome with guilt by the flowers and cheery "get better soon" messages he kept leaving, I put him out of his misery. I used another well trodden phrase - I'm just not ready for commitment. Looking back, all is clear - I just wasn't that into him.

But perhaps women are not ready for such a cold, hard look at relationships, particularly those who secretly enjoy the angst and juicy staff room fodder that a "does he, doesn't he?" relationship brings.

What else are you going to talk about on a dull Monday morning at your desk if you can't anguish over the 1,000 different meanings of the text message he sent after your first date? Women tend to bond in collective anguish over suggestive emails, knowing looks and unforthcoming phone calls.

What's the point plucking petals off a daisy chanting "he loves me, loves me not" if the answer's always "well no, actually, he's just not that into you". And will being armed with this "silver bullet" make women any happier?

Even Liz admits she got annoyed with Greg's sanctimonious attitude at times. "It's easy for him to sit at the lazy Susan of love, and tell me to keep turning until I find just the right dish," she says.

"He's been with his wife for five years and has got a date for every Valentine's Day for the rest of his life. But I do think he's right - most of the time - which is the most annoying part of it all.

"We have been conditioned to expect so little, told not to be demanding, not to seem needy. What would happen if we all started insisting that men keep true to their word, treat us with respect, shower us with the appropriate amount of love and affection?

"I think there would be an awful lot better-behaved men in the world.

"That's all I'm saying."