cool or not?

Yes, it was a good film with a twist that is very hard to detect unless you are paying attention or in fact read it here as I myself did.

That is to say that at the end, Mike (Irons), shouted after Anna as she drove away from both the party and presumably him as she was heading back to the States and didn't want a drawn out farewell as she clearly had no intention of continuing the affair. But of course he shouts out "Sarah", her character name which led me to conclude that he was in love with the fantasy of her character and not Anna at all.

I genuinely wouldn't have noticed this had I not read about it here which is very remiss. I would say that my excuse was that I was accustomed to hearing Mike shout Sarah's name in the film they were starring in but actually he addressed her largely as "Miss Woodruff" so I have no excuse at all for not noticing that. I think maybe they should have had him shout "Miss Woodruff" actually - that would have made it more obvious...lol.