Cat City — Patti Larsen

Ten-year-old Susan's parents dragged her away from her friends to spend a wet and dreary summer in a new place. Unhappy with her new, boring life, she adopts Tucker, a butterscotch tabby, thinking he is just an ordinary cat. But when he rescues her from the rats and brings her to his magical city deep underground, Susan falls head first into a war between the enchanted cats who live under her house and the evil rats who want to claim Cat City for their own.