Oxford needs to make sure its copyeditors drink all of their coffee before starting their work.

Mahtab It's a mistake. I am a native English language speaker and I would never say "a action film". Hope this helps.

An action film is correct - no doubt about it.

And I guess the problem is with the Iranian censorship officer who may have been drunk while changing the words. Could you give me the page number and the book level?

I would say "an" because action starts with a vowel. We also say " an apple / an iPhone"