Beginning with a treatment of how "victims" can be turned to Nurgle (denial, fear, desperation, resentment, bitterness), the book demonstrates that these aspects of emotion can readily lead to vitality, life and energy. It is this juxtaposition that is often over-looked by those who do not discern the full nature of Nurgle. This early part of the book is very well done -- highly analogous to the excellent way in which the Slaanesh volume treated its god. The worship of Nurgle is illustrated by example through consideration of how the Old World comes to worship this otherwise repulsive god.
In the same manner as the other books, some of the tangents in to the various characters and tribes of the old world can be tedious, but there are gems contained within that make it worthwhile to go through. The section on Nurgle's Rot is (of course) obligatory, but well-received. The low point of the volume for me though was the inclusion of the Beastmen. They're not especially Nurglesque (well, some of them are, true), but it is space that could have been spent illustrating different aspects of Nurgle.
The book is rounded off by looking at the daemons of Nurgle and (if I'm honest) all too little 40k references. So whilst the volume is stronger than the Khorne one, it is not quite at the same level as Slaanesh.