The first half is already pretty interesting, and then the second half I think is what makes this special. It's a crazy technical achievement, having one take that lasts nearly an hour, and to incorporate both a child actor and an animal into it was insane, if the old adage about not working with children or animals is to be believed.
But the first half shouldn't be discarded, as it contains some striking imagery and a few scenes that themselves are comprised of li takes (just not nearly as long as that final long take).
It's hard to say what this is about sometimes, and I think I began finding it more engaging when I stopped worrying too much about the plot. It works well enough as an experience - with its impressive visuals and the excellent and haunting music - to satisfy.