This is more of a play than a film. It's talky and claustrophobic, to the point that when at last it moves to an outside scene, you almost feel like you're breathing in cold fresh air.
Interest is sustained throughout, not so much by way of events, as by the interactions of the three very different sisters, and the few peripheral characters that surround them. Dealing with the impending death of a parent, this will (maybe) touch a nerve with some, and give others more fortunate (maybe) an insight to the dynamics to be expected. But I did not find it at any time morose or Maudling or over emotional, the occasionally amusing scenes kept it in check.
My only criticism was near the end, where a 10 minutes or so scene, could/should have been omitted IMO. For me it just interrupted the flow and broke the rhythm of the previous hour+.