By Mary Campbell Dublin

Cecilia Ahern has not even finished her first book and she has been offered a million dollar book deal.

"I haven't slept, I haven't eaten, I can't believe it," said the 21-year-old Dubliner who is the younger daughter of Ireland's Prime Minister, Bertie Ahern.

The book - PS I Love You - tells the story of a 29-year-old called Holly whose boyfriend Gerry dies of a brain tumour.

He leaves her a letter for each month of the year after his death in which he details things she needs to do to improve her life.

Cecilia admits its a real tear jerker.

"It is a heart-breaking story but I try to make it heart-warming as well," she told RTE.

And writing seems to just come naturally to her. She says she wrote her first book when she was 14 and has always enjoyed writing poetry and short stories.

Famous father had no part in deal

"I never showed it to anyone, it was just a hobby, something I liked to do."

Cecilia finished a journalism degree last year and decided to work on her novel.

She admits to burning the midnight oil and starts to write at 2300 and finishes around 0730.

After all the excitement she now hopes to settle down to finish the novel which will be on bookshelves in the spring.

"I have the last line in my head, it's just a matter of writing it," she said.

Her older sister Georgina is already familiar with the fame game.

She has been the girlfriend of Nicky Byrne of pop group Westlife and is frequently featured in Ireland's newspapers.

They got engaged at Christmas after he proposed in the local pub, but now it is younger sister Cecilia's turn to have the limelight.

Ms Ahern's agent said the literary contracts had nothing to do with her father's position, as the publisher who clinched the deal did not even know she was the Irish prime minister's daughter.

Cecilia has also paid tribute to her mother Miriam.

"My mam was very supportive. She advised me to concentrate on writing and to think about getting a job afterwards," Cecilia explained.

Her mother also encouraged her to seek an agent and she contacted a publicist friend who put Cecilia in touch with her agent, Marianne Gunne O'Connor.

The agent sent the first 10 chapters to a number of publishers and HarperCollins was the first to sign up with a reported �100,000 two book deal.

The American company Hyperion has also agreed a two-book contract. The US publisher is a division of Disney and publishes general interest fiction and non-fiction books for adults.

It will publish a book by Sex And The City author, Candace Bushnell later this year.

Cecilia's agent is also negotiating with European publishers and there is even speculation about Hollywood interest in transferring the book to the big screen.

Cecilia joins a long list of Irish authors who have secured major deals in the United States for their first books.

In October 2000 a Wexford school teacher, Eoin Colfer, won the largest advance ever paid to an unknown writer in Britain for his children's book, Artemis Fowl.

Penguin secured rights to the book in a contract said to be worth �500,000 ($804,000) and a �350,000 ($563,000) film option was secured by a production company.

Having secured the book deal Ms Ahern must now get down to finishing her work and hope that it will appeal to readers.