Very interesting approach. Even if you haven't read Campbell before, this book introduces some of his ideas in an easy to digest way. Some examples are quite far fetched, like the function of the Shadow archetype in the plot of The Sandman, but in general it is a very interesting book, contributing to the discussion on comics studies.
The only disappointing thing for me was the last chapter. If you give such a serious and interesting analysis throughout the book, why spoil it in the end with giving details of your personal depression and how The Sandman helped you get over it? How is that related to Campbell and why should it possibly interest me?