I hope this post is not "out of line." If it is, I apologize. Does anyone know this "mystery piece"? I found it in a book I have. Is it an original piano solo? In your opinion, is it worth learning? I don't know much about 20th century music. There are a couple of errors in the performance as I am sight reading it.

John, did you ever find out what this is? It's really weird and probably going to give me nightmares. It's some kind of children's nursery rhyme that has gone awry.

Monica, it's Polka From "The Golden Age Ballet" by Shostakovitch. I assume it was originally written for orchestra but am not sure. The version I have says nothing about "arranged by" or anything like that. So I wondered if this is considered a composition for piano by Shostakovitch. If it is, it's my first Shostakovitch piece.

Yes that ballet is for originally for orchestra, a funny story about a Soviet football team touring the west and being prone to all manner of capitalist temptations. The piano version you play is Shostakovich's own, I believe. And pretty well played too (what do you mean 'learning it' ??? ).
Ultimately it needs to be a bit quicker and more casual, it's really quite an amusing little polka (you should hear the orchestra version).