Books similar to the cat who series

I'm trying to find books for my great grandmother that she will read and enjoy.

She likes mysteries, but I think she has some trouble with longer or more detailed books; she also likes animals, especially cats.

She liked the John Grisham books, but it doesn't seem she reads them to the end anymore.

I know she likes all of the Cat Who books by Lilian Jackson Braun a lot, and has read them all through many times.

Thanks.