i like many of the hardcore dune fans will not read past the first book. Overall, it is amazing because of the universe he has created. There is a language and many, many cultures and worlds(planets literally) he has created.

His story is somewhat along the lines of a messiah and so in that context it is spiritual, but he has said that everything that he has written, whether it be spiritual in nature or something that seems to be supernatural can be explained away by science or common sense.

The first book is great because it combines these elements along with a love story, a complex political climate, structured class systems, creatures and many, many more things all into the first book which he builds on in the series.

The book has its own glossary to define the terms used within. I just can't say enough and i try to read this book once a year..