A great book full of grand themes.
Time has only made it grander in its vision. I mean, there was a time when Islam wasn't the great, dangerous "other" to Western eyes. Moderate Islam had an appeal to the west, for example, Goethe's west-eastern Divan. Dune stands in this tradition. It describes a world which is full of Islamic thought. It is world in which Islam probably pushed aside Christianity to become the world's leading religion. In demographic terms, Herbert will most likely turn out to be correct. Also, Paul Atreides is a soldier as well as a religious leader, that means, he is not a Jesus figure (who was not a soldier); he is a Mohamed, the leader of a state and of a religion. Then there are the themes of climate change, genetic engineering, the artificiality of religion, which were prophetic. Herbert had a keen eye for the themes that would dominate the next decades (centuries?)
If you're into stuff like this, you can read the full review.