In the neighborhood, children and their pets are going to have a pet parade. Andy normally goes with Simon his cat and Simon hates it. This year, Baxter (or Beast) is going to go with Andy, but Simon is kind of nosy and wants to know what Baxter and Andy are going to be dressing up as for the parade. Only Baxter won't tell and it's driving Simon nuts.
It is a cute little chapter book, good for 2nd or 3rd graders. It was engaging enough for my son not be scream and throw a tantrum about reading with pictures to not be too intimidating for young readers--I know this was a thing for me when I was little and why I didn't read many books in the younger grades unless I was forced to. It's also written in letters from and to Simon which is different and fun altogether.
I enjoyed the characters enough that (and the fact that the letters were delivered by a snail mailman, very punny--or how a crow's name was Edgar Allan Crow) that I would be interested to read (or have my son read) the rest of these books.
One thing that kind of bothers me is that some of the characters (mainly Baxter) doesn't spell things accurately, which can throw young readers off a little in a similar way Junie B. Jones does--though they are different. I found that I need to tell him what some of the words meant, like "cuz," because he didn't know what it was. Most of the characters write accurately in their letters.
Over all though, the story was cute and gave me a reason to explain things that had gone over my sons head. Like SnailMail, Edgar Allen Poe, and who Sherlock Holmes is, which got him a little more interested in what what/who those things/people were.