Paul is depressed, and rightfully so. By going along with the layed out path the bene gesserit planted amongst the fremen on dune the jihad has come to past, and caused destruction all over the galaxy. Paul is the most powerful and at the same time the most powerless man in his own empire with foes plotting to overthrow him. 

More a political game of chess then an action filled battle of the previous book, I thought the moral and philosophical points of religious takeover, governmental ideals and what it is to be human once more was a good addition the the first book, highlighting how Paul was both savior and the downfall of the fremen, bringing water prosperity and poisoning the very way of life and ecology to the fremen and arrakis. 

Paul both dying and forever living on after losing chani, but also leaving Alia with two parts of him and their parents and chani will make for an interesting sequel. I’ll continue reading children of dune to see what happens to this world.