Being the last book in the series: Chapterhouse: Dune carries a lot of narrative weight. This book is interesting on a number of levels and frankly it blows Heretics Of Dune out of the water in terms of the depth of the characters and the narrative details it contains. The sixth book in the Dune series is focused on the Bene Gesserit and how they are contesting with the hostile forces from the scattering that are set up in the previous book. 

One quality that Chapterhouse: Dune shares with Heretics Of Dune is that the book charters are mostly constrained to a smaller number of physical locations. The Mother Superior Odrade lives on Chapterhouse. This is the name given to the planet on which the Bene Gesserit have staked the fate of their order. Even more constrained are the characters Duncan Idaho and Murbella who reside on the no-ship which protects them from being discovered on this planet. 

There are so many things to get into about this book but many people when analyzing it online tend to focus on the ending. This ending is set up throughout the book when Duncan begins to have weird visions of a couple that does not appear to be anything he has ever seen before. Many people interpret this to be a representation of Frank and his wife Beverly. Beverly was a large influence on Frank throughout his life and I recommend you check out the video on the home page about Frank Herbert to get a more impactful summary of all the ways Beverly influenced and inspired the Dune book series.