What an amazing novel. To call Dune science fiction would unnecessarily restrict its importance. It is a genre-defining space opera, drawing on elements of scifi, ecology, theology, and “PPE” – politics, philosophy and economics.
Dune is set in the distant future, where it is forbidden to make machines in the image of humans (i.e no AI or humanoid robots). In response to this, humans have evolved special abilities: superior logical reasoning, exceedingly fine control over one's musculature and mind, or even limited prescience. Society is medieval, with feudal Great Houses operating under the galactic Emperor. This plot decision allows Herbert to focus much more on the politics between houses (similar to A Song of Ice and Fire, or so I'm told) rather than advanced technologies. Economics also plays a key role: the events of the book are precipitated by the planet Arrakis' monopoly on "spice", the mysterious substance that enables the aforementioned special abilities. Another faction – the Spacing Guild – controls all interstellar space travel, arguably making them more powerful than the Emperor.
I wouldn't say that Dune is a particularly complex book – it doesn't require scifi experience to enjoy (unlike some of PKD's work) and doesn't require a deep buy-in to the worldbuilding (unlike Tolkien's Silmarillion or similar fantasy). However, there are still several layers to enjoy beyond the main plot (compelling as that is): the small distinct mannerisms of different houses – how the antagonistic Harkonnens constantly think about others' pressure points while House Atreides emphasises loyalty, the subtle motifs of revisionist history, the parallels to Lawrence of Arabia and his role in the Arab Revolt during WWI.
Dune may look like a long book, but it was highly readable. Herbert embeds a masterful balance between foreshadowing and surprise, making each page a pleasure to read. Definitely worth the time.
“I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain.”
**EDIT (March 2021): ****I really have to stop re-reading this book!