Really rather good. It has been pointed out that Glenn Close does look a bit like Robin Williams at times, but she's excellent. The pace is slow, and not in a bad way, no screaming drama, though it still had me in agonies of speculation about how it would end.
Janet McTeer steals every scene she's in.
There's a unintentionally very "Little Britain" moment in the film which I'll leave for you to spot and chortle over.