Wonderful, this is.
It is wonderful in part because it takes chances with the material and the presentation.
You have to appreciate a few facts. This was Agatha's first published book. It is before she hit her stride where she was comfortable enough with the genre that she started fooling with the rules of the genre in amazingly clever and modern ways. So it is just a typical complicated murder, planned by "evil" people. The murder itself is conventional for the period, like hundreds of other books of the period.
It introduces Miss Marple, so it is apt that the story lines include our introduction to the character, adding elements that are from Christie.
Another fact is that Christie during this period had unhappy romantic episodes and had some intrigue and mystery in her own life. She would in fact be very much like the young Marple we see here. And inserting the author in the story as the detective is precisely something she might do herself. (The adapter here also plays the coroner. Nice metafolding.)
If you are going to watch any of these, you should watch this one first to get the backstory on Jane, and to understand why she wistfully looks at an old photo.
As to the mystery story itself, it is background noise and poorly presented. But remember it is so in the book. On that we have famous actors doing their stuff. One of these is Jane Asher. She's not an amazing actress but she if often used as an amazing presence. And here it is so. She plays a character that if I recall is more prominent in the book, but less sassy and obviously significant than rendered here. She's one of the most remarkable unremarkable women in modern history because of her role in the Beatles and Alice.
Something along these lines may be done one day for theatrical release, and I expect similar notions of narrative folding and cinematic exaggeration. But we'll have more explicit recognition of what drives this story, and presumably the whole village: sex.
Ted's Evaluation -- 3 of 3: Worth watching.