I have not read this book, but the title caught my attention. Because I had heard about mail delivered by pigeons, horses... even dogs, camels and reindeer! But cats??
I thought, at first, it was just a children's books. And it is, but inspired in a true event. In the late nineteenth century, some people of Liège (Belgium) decided to free some cats in the countryside, far away from the city. In less than 24 hours all the felines were at home, claiming for being fed. So they deduced (?) they would train 37 cats in order to deliver mail.
As you can imagine, the the experiment did not turn as expected: the cats suffered from lack of discipline and interest.