One word: perfect. But do read on.
I know that if you have heard about this movie, you have heard about how it has an authentic Agatha Christie-style plot. Yes. They are all right. It is exactly like an Agatha Christie. For some time, I really thought it was based on one of her books. But no. This is completely independent of Christie.
It is an amazing and perfectly-plotted movie. A movie which has two big action stars as its main characters with literally no action. None at all. Not the kind of action you'd expect of them anyway. They have both acted to perfection. The direction, the cinematography! Ah! It is all perfect. Go watch it. Now! By hook or by crook. Especially if you are an aficionado of extremely brainy whodunits. 'Especially' especially if you are a fan of late Christie. You will absolutely love it!! Happy watching!