Being Mortal: Illness, Medicine and What Matters in the End by Atul Gawande. His argument is that for the last thirty years the combination of advancing technology and prosperity have made it possible to prolong human life in ways that would have been thought pointless not long ago. Instead of asking how people ought to die, his book asks how people ought to have the best life they can, given the lottery of longevity.
I'll be honest. I screwed up my eyes and skimmed during the passages when he was describing the awful conditions that had been endured by patients he'd come into contact with, ranging from people who came into his hospital to his own father; on the other hand I was paying maximum attention when he got to the bit where he described the moments when the treatment paused and he had The Conversation.
That's the main thing I took away from "Being Mortal". What matters is what a person wants out of life. Once you've got that from their own lips you can work out how long they can have it for and how it might best be provided.
Ten years ago, I took our then ailing cat to the vet. I said "is there anything you can do?" As soon as the words were out I realised that was a ridiculous thing to ask. There's always something they can do, as long as somebody's prepared to foot the bill.
Read it. If you dare.