The Story of Diva and Flea, written by Mo Willems, illustrated by Tony DiTerlizzi, Disney-Hyperion, 2015.
I bought this book for my seven-year-old son, and took it with us on vacation, and every night I read a chapter or so to him. The next morning, he would re-read the same passages himself. He LOVED this book, so I'm letting him write the review:
"I liked this book because Flea is a beautiful black and white cat like our Buster. And Diva is a white dog that looks like Piper, but is white like Ellie. She was more like Piper than Ellie, though. My favorite part was when Flea and Diva became friends. And I really liked the cloud-cutter because Paris is my favorite city. And I liked the friendly feet at the end of the book. The drawings were SO good."