I read the short story when I was a lot younger. It was about an older gent who was so bored with his everyday life (and nagging wife, rhyme not intended!), that he would create elaborate fantasy lives to escape into; such as secret agent, or WW1 fighter pilot.
I remember the story being quite funny, but ultimately rather sad, as the poor guy just couldn't be satisfied with regular life. I am very curious to see how the movie will compare to the short story, which was written so long ago (1939!).
I think I need to re-read, before seeing the movie!