Really good analysis. I also found it very interesting that the main character never spoke for himself, that we just heard from Dr. Jekyll oder Mr. Hydes actions by other people.

Hello from France! Yes, the book is "A child's garden of verses", and "my shadow" is about a little boy who tells all the strange things his shadow does.

I had this book, don't remember the poem specifically (something with a candle?) But it's called a " Child's Garden of Verses"