The body in the library a Miss Marple mystery

Not sure how many Miss Marple's I've read but I was always surprised at how she picked up on things. I know she's imaginary, but still.

I found the plot complex enough to keep me focused on the story at the moment, and I don't think I figured out who it was until the last few paragraphs, which is how I like a mystery. And I'm so thankful the story isn't as dark and gory as many of the more recent authors are!