Pointless story with wasted potential.
This is a weird book. I'm glad that it has a pronunciation guide for the name of Mxyzptlk, because otherwise you'd have no idea how to pronounce it. He's kind of a weird Superman villain. I guess there's kind of a conflict in that the pranks that Mxyzptlk plays are possibly dangerous and deadly, and Mxyzptlk doesn't seem concerned by that. But Superman isn't really doing anything terribly interesting.
He doesn't have to make any decisions beyond figuring out how to solve the problem. That only works because Mxyzptlk's pranks are very literal. Something inflates like a hot air balloon, and Superman blows freeze breath at it to cool it down so it doesn't fly anymore. It's weird. The illustrations are good. It doesn't seem any more or less interesting than any other books. It's pretty bland as far as a Superman story goes. Nobody dies or gets hurt.
Mr. Mxyzptlk comes, plays a bunch of pranks, Superman saves the day. There's no real message, which is strange for Superman. You would think that they could come up with some kind of message, but it's not even trying for a message. Maybe that's good.