This short novel, or maybe it would be classified as a novella is about two cats that lives with Mr. and Mrs Neal in a house in a town....somewhere. They are well taken care of cats, they gets treats and meals and taken to the vet when they don't feel go. But they also are kept inside because the Neals worry that they might get lost of hurt if they go out into the world. The Neals have used water to convince them to stay indoors, but being pelled with water only makes them want to figure out where the water comes from and how to escape being hit by the water.
On top of that, the two cars are brothers and work together nicely. Marco can read from seeing the newspaper on the bottom of his litter box. While Polo can't read, he is really not as bright as Marco, but he is very quick. So the two of them eventually figure out how to avoid the water and go out doors and set out on a great adventure.
They meet other cars, some are unhoused but others have homes where they are given the freedom to go. They even have a club where several of them spend time together. Marco and Polo are new on the scene so they have to prove themselves to the gang by finding the answer to a queston. In the process they find themselves doing some really frightening things and seeing a lot of the area in the town.
Finally they go back home, are welcomed back by the Neals, but now they have two additional young cats and we, as the reader, get a glimpse of other future adventures for both the original pair of brothers and their younger "house mates".
This is really a middle to rather on the young side "adult" reader so there is no real complexity to this story, but if you like cats and "getting into their heads" it is fun brief read.