Mary Poppins was the first hard cover book I partially read by myself. My dad starting reading it out loud and then I took over reading quietly for myself. I recently started listening to it on a audiobook.

I second the recommendations for Astrid Lindgren and Tove Jansson. Yes, hu-u-ugely popular in Russian translation, both of them and especially Lindgren, but unfortunately not in the US.

I will add: "The Blue Bird" by the Belgian playwright Maurice Maeterlinck.
It is a play. I saw it in a theater, probably my first theater experience as a child. Was mesmerized by it. Also recently started listening to it on an audiobook. If you cannot find a play performance next to you, you can still read it for yourself or out loud. Here is the full text for free:
The Blue Bird, by Maurice Maeterlinck