This was a reread - Obsidian Blue and I did a buddy read of this one back in 2016. I remember that I enjoyed it, although I think I enjoyed it more this time around. I find that to be a pretty consistent theme with Christie - my expectations are really high going in, and then I'm pleasantly surprised but not Murder of Roger Ackroyd gobsmacked so I underrate it my mind.
When I go back to read them again, though, I am usually much more impressed, which was the case here. Miss Marple has aged quite a bit by this 9th book in the series, and took a fall which resulted in her being subjected to the indignity of a home nurse who talks to her as though she is a toddler. She also has a new housemaid, Cherry, who is a delight. She's not a very good housemaid, but she gossips and cheers up Miss Marple immeasurably. At the end of the day, Miss Marple decides that a cheery smile and a warm attitude is worth more than spic-and-span floors. I agree with her there, as the state of my floors would demonstrate.
Inspector Craddock features prominently, as does Dolly Bantry, who has moved out of Gossington Hall after the death of Colonel Bantry. She remains singularly obsessed with herbaceous borders, which is the most English thing I can think of.
There are some similarities between this one and both They Do It With Mirrors and Ordeal By Innocence - there is a wealthy, self-centered woman with a motherhood complex at the center of all three of them. Christie has used this trope before - woman who isn't really suited to being a mother, because of social pressures that place motherhood as an essential element of womanhood, buys herself a few children that she really doesn't want. She then either grows bored with them after a time and passes them off to someone else, as in this case, or she destroys them by neglecting their needs in some specific way.
Both the victim and the murderer were fascinating in different ways, and while they were both extreme examples of a certain type of person, they were also believable. Overall, I enjoyed this much more on the reread.