This book was Miss Marple's Greatest Hits.
It's a book of short stories in which Miss Marple is clever, self-deprecating, and draws her village parallels to solve mysteries framed in the form of "problems" at a dinner party. The other members of the party tend to come up with outlandish or complicated solutions to the "problems," but Miss Marple sits, knits, and gets to the heart of things.
I figured out some of the short stories, but not all. It was very nice to just watch the clever lady think and try to convince folks that people are the same, due to their nature, whether con artists or petty village thieves.