For her legions of fans, the new film of Cecelia Ahern's bestselling book P.S. I Love You is a dream come true. Starring Hilary Swank and Gerard Butler, CAHIR O'DOHERTY talks to the amazingly successful young Irish writer about her career to date.

By the time Cecelia Ahern reaches the lobby of Manhattan's swank Parker Meridian Hotel on 57th Street it's still morning, but she's been awake since 5 a.m.

Wearing heavy makeup from her promotional appearance on Good Morning America hours earlier, she's dressed to the nines in a designer black dress and red overcoat, looking every inch the young media mogul she's become.

This month Ahern is in New York to promote her new film, P.S. I Love You, based on her first best-selling novel, and also to promote her new book, There's No Place Like Here. (The film opens nationwide on Friday, December 21.)

If she has any time left over, she'll probably pour over the scripts of her new ABC television show called Samantha Who?, which last week earned its star Christina Applegate a Golden Globe best actress nomination.

On the face of it, that's enough success for three major writing careers, because Ahern is producing a book, a film and a TV show at the same time. But before you start clawing yourself with envy, just her just have a look at her crazy schedule: today she's in Manhattan with Diane Sawyer, yesterday she was in Los Angles with Hilary Swank, the double Oscar winning star of P.S. I Love You.

Next week the Japanese film industry want to fly her to the Tokyo for the film's premiere, and then the Germans and the Italians want to do the same the week after. At this rate she'll be lucky if she gets home to Dublin before New Year's Eve.

With all of these demands on her time, the big question is - is she having any fun?

"It's just the way I am. It's the way I grew up, like," says Ahern, still only 26, during an interview with the Irish Voice. "I mean, it's all fantastic but it's nothing more than what it is. And it doesn't make me any more than what I am.

"When I step back I think, Oh my God all of these things are incredible and I can't believe they're happening, but you can't really see yourself as any other thing than the person you are, you know?"

Not everyone has toasted her success. It's been fashionable in some literary circles to think of Ahern's books - she's got three internationally best-selling novels under her belt - as insubstantial.

There's no doubt she's received her fair share of bashers all too willing to call her books fluffy chick lit or worse, as though they tackled nothing more challenging than where to find the best place to buy a new Hermes scarf. But the truth is that people who sneer at Ahern's work usually haven't read her.

Ahern's books are surprisingly mature - and sometimes wrenchingly sad - both in terms of their subject matter and treatment. She's rightly famous for her observational skill, but she's equally good at creating instantly believable characters, and there's more than a little emotional wisdom animating her tales.

Says Ahern, "When I first wrote P.S. I Love You some people said how on earth could she know about issues like love and death and what they do to you? She has no life experience.

"But what I'm writing about are emotions we all share, and although I didn't lose a husband it doesn't matter. You don't have to kill someone to know how to write a horror story. The writer feels things and writes about them. I think it's fair to say I have an old head on young shoulders."

Ahern admits that the storyline for P.S. I Love You came from a dark place. Writing the story she felt she was battling her own fear and sadness and every negative experience she could think of - and her struggle as a writer was to make the story a little more hopeful, and to find some redemption for the book's hero, Holly - and in a way for herself.

Says Ahern, "People have said to me you're very brave to tackle a subject like grief. But it came to me and I just had to write it down. It was just all very natural, as it should be."

The heartfelt romance that blooms between Holly and Gerry in the film - and then it's shocking loss, due to the death of one partner - is underlined by the appearance of a fledgling suitor played by Harry Connick Jr. who knows he doesn't really have a chance to replace the man Holly lost.

Although she sold the rights to her novel not long after it became a smashing success, Ahern insisted that Warner Brothers did not spoil her original story with a sappy Hollywood ending.

"For me love stories are never about the girl getting the guy. A happy ending for me is when people get to a point when they feel like there's a possibility for a new life. When they wonder if maybe they could fall in love again," Ahern says.

"In losing Gerry, Holly has lost a huge part of herself. Her journey is to find the ability to heal and move on. I hate those predictable Hollywood endings that trick or cheat you, or try to pretend things aren't as hard as they sometimes are."

Although Ahern knew from the beginning - as soon as the deal was done - that she wasn't going to have any involvement in the final script, she didn't worry. She was resigned to the fact and admits that at that early stage of her career she would not have known what to do with it anyway.

Ahern cried for two hours after seeing the finished product. It wasn't just that she liked what she saw, it was the fact that it had been filmed at all. Add to that the epic beauty of the Irish landscape and her heart just filled with a patriotic pride in her homeland.

Says Ahern, "I know you hear all this moaning all the time from writers who say the final film is not like my book. But I think if that's going to be the case don't sell the rights, you know?

"I was aware of the fact that it could be very different, but I just kept being positive about it. It was an exciting thing for Warner Brothers to buy my book so I wasn't going to say no!"

Though Cecelia has earned fame and fortune very much in her own right, it would be remiss not to ask about her father, Bertie, who happens to be the prime minister of Ireland.

Asked if she was bothered by personal questions about her famous father or other well known family members she replied, "Well my dad is who he is who he is so people ask me about him. And (sister) Georgina is married to pop star Nicky Byrne of Westlife, so I can understand the curiosity, and I really don't mind being asked."

Bertie, Georgina and Cecelia's mother Miriam are regularly asked about the young novelist in their family just as often. "They never describe me as fluffy, that's for sure," says Ahern.

"I mean I'm always happy, always cheerful and I'm a very positive person. But absolutely I have my dark moments and that's a part of what drives me to write.

"There's a huge amount of my own journey mirrored in the journey that Holly takes in P.S. I Love You. Stuck in pajamas, won't leave the house all day, that's actually what I'm like when I'm writing. When my family come around and say, 'Come on let's go out' I'll reply no, no, no. I'm still writing - that's in the film and that's also my life."