I never knew that Miyazaki did any mangas--before I read this, his name was synonymous with anime movies such as Princess Mononoke and Spirited Away. I was interested to read this, because I read that it was done before many of his other works. I began to read Shuna no Tabi with the hopes that it would be as wonderful as Miyazaki's later works.
I was not disappointed! The art is done in the beautiful, typical Miyazaki style--even fully colored! The art was stunning. I can't imagine how much time he must have put into each panel. The character development is sufficient for a short story of this length, but I wish we had gotten to know the backgrounds of Thea and her sister. You end up loving them, even though you don't know them well. And from the beginning, you are rooting for Shuna on his journey.
This manga is very different from others that I have read in that the story is mostly told through the art and some narration. There is very little dialogue. Still, the story flows smoothly and it is easy to understand. The lack of dialogue adds to the fairytale-like feel of it.
You will notice that many elements of this manga show up later in his other works. I think Shuna was used as the basis of Ashitaka's (Princess Mononoke) character; the two look almost exactly the same and both ride a reindeer-type creature.