Which Irish author wrote the best selling book 'PS, I Love You'?

Cecelia Ahern (born 30 September 1981) is an Irish novelist and has been writing since 2004. She has published several novels and contributed a number of short stories to various anthologies.

Before starting her writing and producing career, she obtained a degree in Journalism and Media Communications from Griffith College Dublin, but withdrew from a Master's degree course to pursue her writing career.

In 2002, when Cecelia Ahern was twenty-one, she wrote her first novel, PS, I Love You. Published in 2004, it was the number 1 bestseller in Ireland (for 19 weeks), the United Kingdom, U.S., Germany and the Netherlands. It is sold in over forty countries. The book was adapted as a motion picture directed by Richard LaGravenese and starring Hilary Swank and Gerard Butler. It was released in the United States on 21 December 2007.