To give an analogy, I could compare the effect of this book with that certain advertisements. Sometimes, in fact, that children or even adults go about certain occupations when suddenly their attention is drawn to the left on TV screen; music, or even a sudden silence the plot and leads them to suspend their activities. The vision of this book provokes my children a bit the same phenomenon.
It is true that reading this book to his children also proves enjoyable for adults, even after multiple repetitions, giving it a dimension somewhat magical.
The story is touching and is clearly dreaming. What more? A classic? No doubt if most children respond like mine.
Feel free to offer your children, if you do not know yet. I am convinced that they will love. And do not worry; I do not see how the illustrations may seem depressed. On the contrary ... (but to each his opinion).