If you like Joe Grey mysteries
There are several in the Joe Grey series, in case you haven't read them all. Here are a few other suggestions:
The Cat Who Could Read Backwards by Lilian Jackson Braun.
Reporter Jim Qwilleran is so anxious to get back to work that he accepts a job covering the art world for the Daily Fluxion. When various people turn up dead, only Qwilleran and his "partner," Koko, the Siamese cat, can find the answers. There are about 20 books in this series now-so if you like this first one, there are many others to keep reading!
Murder on the Prowl by Rita Mae Brown.
When two obituaries appear in the local newspaper, people are a little surprised when the subjects turn out to be alive. Surprise turns to shock when those two people later turn up dead. Mary Minor "Harry" Haristeen, with assistance from her cats, Mrs. Murphy and Pewter, and dog, Tucker, are determined to find the culprit. This is another series ("Mrs. Murphy Mysteries"/Sneaky Pie Brown) - there are a lot of books in this series too. The first one is called Wish you Were Here.
Cat in a Midnight Choir by Carole Nelson Douglas.
While Temple Barr investigates a group of mysterious magicians, called the Synth, her cat, Midnight Louie does some investigating of his own. The Midnight Louie Mysteries are also a series with lots to choose from.
Strange Happenings : Five Tales of Transformation by Avi.
Five original stories where strange changes occur, from a boy and a cat changing places and a young man learning the price of selfishness to an invisible princess finding herself.
Scratch the Surface: A Cat Lover's Mystery by Susan Conant.
When Felicity Pride, writer of cat mysteries, returns home to find a
dead man with a large, living, gray cat in her vestibule, she decides to solve the mystery herself.