The movie is based on the best selling book of the same name, by Irish novelist Cecelia Ahern. Published in 2004, the book reached #1 bestseller status in Ireland (for 19 weeks), the UK, the US, Germany and the Netherlands.
There are many differences between Ahern's book, which is set in completely in Ireland, and the film version of the story which is partially set in New York City. William doesn't appear in the book. Holly has a father who is happily married to her mother. As well as a sister, Holly has three brothers.
A package with the ten letters was given to Holly at the beginning of the book by her mother, along with a message from Gerry that she was only allowed to open one each month.
In the book Gerry and Holly meet in High School and have been together ever since.
Worldwide Box Office: $139,580,373*
*Box Office Mojo