Cat Detectives are very good seller,you just have to think of something that hasnt been done.
How about a Pet Squad,with a Cat,Dog,Bird Hmaster,Monkey,Horse each contributing thier strengths to solve crimes.
Inspired a bit by the Freddy the Pig stories of my youth.
Or a girl,that can become a Cat.
Or can communicate with All Cats,like Aquaman does with his Finny Pals.
A Found Cat Hotel Novel,you could have the rights,free.