I've seen this sort of film before - this sort of ensemble drama taking place at some significant social gathering, often, as here, a wedding - but rarely done as well as here. Rachel Getting Married, it's called, but it's really about Rachel's unstable, unthinkingly self-absorbed, just-out-of-rehab sister Kim, rendered by Anne Hathaway (who I don't think I've seen in anything before, though of course I know 'who she is' in the media sense) in a striking performance which seems to synthesise an intense naturalism with a marked level of craft, and the film's focus remains principally on her, though it's large enough (in canvas and spirit) to also take in the web of relations connecting the various members of her immediate family, and others associated with the wedding, with each other.
Watching it was a bit of a gruelling experience for reasons both internal and external to the film - as to the former, Kim's speech at the celebratory dinner, for example, is up there amongst the most excruciatingly embarrassing, cringeworthy scenes I can recall in a movie (and perfectly set up by what has come before), while as to the latter, I started the film with a headache which only worsened with the hand-held camera-captured progress of events - but Rachel is an impressive bit of film-making.