Dune takes place in our universe in the very distant future, some 21,000 years from now, when the human population is spread throughout the universe - an impressively conservative amount of time for our technology to facilitate such travel. Curiously, computers have been outlawed, requiring the training of humans to do complex and speedy computations in their place. The political-economic structure of the worlds are petty feudal systems which are declining in power and stability.
The religious overtones are a curious invention. Dominated by women but yearned for a single man to be the messiah. These women, the Bene Gesserit, so called witches exist selflessly for breeding and to support their husbands but they are the true, though indirect, power behind their husbands and they possess the ability to control by mere speech.
Both sides are extremely sexist however there are two couples, Leto/Jessica and Paul/Chani, which seem to bridge the gaps. But Paul is something else all over again. Within Paul, the female mind within the male body, lies all the power of the universe. It is this duality that gives him all his strength.
The possibility of free will is a strange conflict. Paul at times can see into his future but his choices and their consequences lay a veil over the future. Is it possible that Paul can see only the near-future, what is inevitable from the actions that have already been taken. For example, if I throw a rock over a cliff, it is inevitable that the rock should hit the ground. But I cannot possibly know what will happen to that rock in a hundred years.
I find it curious that the leaders of the religion are called Bene Gesserit, which means something like "he/she does good" which is ironic since I am not convinced that this order only does good or is even actually moving toward good. I will need to read more of the Dune series to decide that.