Miss Marple has always been one of my favorite characters created by Agatha Christie. I have read most of her books a dozen times over the last 50 years and have enjoyed a lot of the movies and TV series that has been created to showcase her style and versatile wit with her characters.
There is a wealth of information about Christie and all of her books as well as the characters available on the website: https://www.agathachristie.com/characters/miss-marple