An interesting idea that falls short in execution. The idea of a post-apocalyptic world of the dead was interesting. It has new races, prestige classes, spells, and enough history to provide a start, but it lacks some key, in my opinion, information.
You'll find updates to dwarves, gnomes, elves, and halflings, but no others. On the one hand you can imply the half- races don't exist because they aren't mentioned, but neither are humans. All three are mentioned elsewhere as possible hosts for the Raijin (vengeful ghost PC). So, do they exist in this world of not? One sentence is all that is required to let us know.
There are also no updates for existing classes, which wouldn't be a problem, but the text hammers home, over and over again, that the gods have forsaken this land. So what exactly doe that mean for divine spellcasters? Do they exist? Can they cast spells? In a related text there is one powerful NPC who provides divine spellcasting, but that's just one and doesn't answer the other questions.
I would expect an overlay like this would cover all of these things, and this doesn't. Map, locations, encounters aren't a requirement for me, but the basics are, and this falls short. All that would be required is maybe a half-dozen pages to cover these deficits and I would give it another 2 stars, but not as is.
[2 of 5 Stars!]