The challenge is to think of books featuring "older" protagonists or authors.
My all-time favorite reads are “The Cat Who…” series, written by Lilian Jackson Braun. I have read and re-read them many times. Ms. Braun is now well into her 90’s and, unfortunately, her age has shown in the last couple installments, and apparently the series has come to an end. Great loss for cozy mystery fans.