Group Read, October 2021: Memento Mori

Our October group read is Memento Mori by Muriel Spark. Please join in the read and post any comments on this thread.

I've finished this, my first 1001 book in a very long time.

It seems to be quite a sympathetic portrait of old age and its various trial and tribulations. I thought it interesting how he message was heard and received by the different characters in very different ways. A couple of times I wondered if I knew who was behind it, but I'm not sure that I ever did. The way that events spiral out of the characters' control was quite shocking. And the end is just a bit sad, but true.

I just started reading this and am 70 pages in. I enjoy Muriel Spark's subtle sense of humor. I found myself chuckling at the start of chapter 5:
"Mrs Anthony Knew instinctively that Mrs. Pettigrew was a kindly woman. Her instinct was wrong."

Finished and I would probably reread this book sometime down the road, which is saying something from a person who doesn't reread much. Funny, in a darkly comic sort of way. Great characters. I appreciated the different ways they all approached the phone calls reminding them they must die.
Does anyone have thoughts as to who the phone caller was? Does it matter?