'To those who dare ask why I behave as I do, I say: With my memories, I can do nothing else. I am not a coward and once I was human.'
-The Stolen Journals of Leto II
Book IV ventures further down unpredictable avenues, more so even than the reversal of reader expectations that was Book II. Whereas the previous volumes each had identifiable influences, actions reminiscent of classic tales (Muad'dib as Aeneas, etc), God Emperor isn't so easily relatable. It stands apart, exploring the mind of a man become a god—changed in more than just the figurative sense.
Leto II's current condition grants him an insight into the human condition that had never existed before. It also paradoxically distances him from fully empathising with the people he's closest to. Empathy is a process dependent on memory. Being Atreides means Leto has access to an almost infinite store of memories from countless lives but they're each shaped by the era in which they were formed. His only experience of a society held in the grip of a God Emperor for millennia is from the side of the ruler, not the ruled. His outlook is invaluable but one-sided.
Arrakis is changed, too. No longer just a place to train the faithful, it's the predicted centre of the universe. The Bene Gesserit, Guild and Ixians are diminished but still around, slaves to the planet's resources, biding their time.
It's impossible to know for sure but I suspect the voice of the author is split between at least two of the main characters. With his knowledge of atavistic characteristics and myth structures Leto is, of course, one of them. Using the poetic or prosaic as the situation demands; teaching on an active level, not through repetition; forcing the listener (and reader) to apply what they know as fact and extrapolate into the equation what they think they know in order to fully understand the lesson is an idealised version of an author/ teacher.
As usual, the introduction to each chapter is a commentary on more than just the individual parts, extending instead to the whole. You should also have recognised by now how Frank orchestrates situations for the sequels to follow up on. God Emperor delivers on that. It has a proper ending so you can stop the series afterwards if you want to, but there's still more to the story of Arrakis.
5 reassuring dimensions out of 5