約束の猫、 The Promised Cat, is a collection of four short stories involving cats featuring beautiful illustrations. Its target audience is towards children, but I think people of all ages can enjoy it. There are dark elements to each story, but there is always something hopeful, too.
The first story was definitely my favorite. The second was the weakest in my opinion. The third and fourth were both enjoyable, and the illustrations kept it interesting throughout. I picked up another one of their books as well, so I'll definitely be reading that in the near future. I also didn't realize it was meant to be a children's book at first--the bookstore had them in the adult section--but the simplicity didn't take away from my enjoyment.