History
Right. So, history is really important in a real world urban fantasy setting, because history actually happened and it helps worldbuilding to understand how your various magical creatures fit into known real-world history without changing things.
Some settings do this well, providing a rich and detailed secret history. Some do it poorly, simply tacking on monsters to historical events without considering the actual consequences of this. Zombie: The Coil takes the latter approach.
We start with three different origin myths for zombies. These myths are by no means exhaustive, they're just three variations of the primary zombie religion.
Unfortunately, the formatting here is absolutely atrocious. Each story gets its own column. But each is also four pages long. Meaning that you have to flip through four pages, go back, go forward, go back, and go forward again to read them all in order.
This may have been the intent, to force the reader to read snippets of each instead of the whole thing in order, but it just doesn't work. It does not work at all.
The Zombie origin myth is that a Shaman named Zemi somehow broke mortality, the titular Coil, in a manner that allowed some souls to return to their decaying bodies. Whether this is good or bad changes with the telling. Some see mortality as an unmitigated evil and anything that fights against it is good. Others see the existence of zombies as a violation of the natural order of things. This, however, falls into the bounds of religion, rather than science. Zombie historians only have knowledge going back to the middle ages, and didn't start keeping detailed written records until the Civil War.
Zombie academics are a thing.
Where it really breaks down is in the hounfars. The events that involved massive numbers of dead spontaneously coming back to life as zombies. There are a lot of those.
The black death, for one, was supposedly a massive event in Zombie history, but it's not spoken of in detail because there are no zombie records of the time. It's just that a third of Europe died and a fuckton of them rose as the walking dead, to the point that whole villages full of mindless zombies had to be put down by the authorities. Zombies should have been common knowledge then. This makes the current masquerade rather implausible.
The Civil War is when recorded Zombie history starts. And it involves a zombie underground railroad organized by older zombies using zombie telepathy, which can be fairly long ranged if you train it. This zombie telepathy, called the Pulse, is used as an explanation for why Zombies are always able to tell the difference between other zombies and living humans, as well as how zombies who have no mouths can talk. The idea is that the established zombies took in the young ones and the mindless ones, to teach them the ropes and keep the masquarade intact. But, again, it leads to a rather weak masquarade, if given war battles give rise to zombie hordes, someone will notice. The story expects you to believe that this can be kept under wraps by staying on top of it and having highly coordinated teams of troubleshooters swoop in whenever it happens. This is a huge stretch.
The World Wars make it an even bigger stretch, but they're the canonical beginning of modern zombie society.
The in character narrative presents the Jackals as wrong for preferring to kill mindless zombies instead of taking care of them. But, we're talking about thousands-strong hoards of Nazi Zombies and Allied Zombies. It's impossible to reasonably keep them hidden and fed.
Surprisingly, there aren't any Nazi Zombies in this game.
After WWII, the new zombies started organizing themselves into like-minded groups. This wasn't a major thing before because of the tiny number of living dead. This makes some sense, though one would expect that a group with both a stringent masquerade that requires a great deal of effort to keep and a long-range communication system would organize earlier than that.
Society
This is the chapter where it becomes very obvious that this is a fan splat, and one that was only lightly played.
Old school RPG settings tended to be people's homebrew game settings. The Forgotten Realms was Ed Greenwood's home D&D game. Greyhawk was Gygax's. Its easy for these guys to throw out interesting NPCs and compelling events, because it's shit that actually happened at their tables, and the big penis NPCs are their PCs, more often than not.
This is one of the reasons that it's a good idea to play the game for a while before writing the setting book.
The society chapter is wordy, but simple. You've got your Cadre, which is the fancy name for your adventuring party. These are the guys that you hang out with, and it's functional. Your cadre is specifically not a byunch of guys who met in a bar and got together for no reason. They are your friends, personally. They're the guys you hang out with. They're your Chandler, Monica, Joey, and Rachael. This supports a lot of mixed groups, though it necessitates that players talk to each other. The fact that there are only two types of zombies makes this easier. There's no reason why you can't have a mixed Jackal and Grande group, general racial tensions aside.
Population
Zombie suffers from the same problem as Vampire, and suffers from it worse. There are simultaneously too many zombies to go unnoticed and too few zombies to have any sort of politics. There are 20,000 zombies in the world, give or take. The ratio given, officially, is 1:300,000, which was meant to be three times as rare as a vampire.
Every Grande basically has to kill people regularly, more often than a vampire does. While it's possible for one to feed without killing, it's impossible for one to feed without causing grievous injuries, and random cannibal attacks are a kind of obvious thing that get in the papers.
And yet, 20,000 zombies spread out around the world means that your cadre is probably the only group of zombies in your city.
It's worse in that the fluff doesn't support these numbers. Necromancers and random walking dead hoards are both major problems that your cadre is likely to encounter.
Race Relations
Is extremely bare bones. Most Jackals think that Grandes are murderers. Most Grande's think that Jackals are gross angry cannibals. Lots of people give zero fucks. Your cadre probably gives zero fucks, because mixed games are inevitable.
The Revolution
This is another place where scale fails. Zombie slavery is a huge business. There are plenty of slavers who just grab mindless zombies and put them to work in the fields, using magic to control them. Some skilled necromancers create new zombies instead. The slavers outnumber and outgun the living dead, but there is a major guerrilla war going on between the two, with zombie strike teams raiding slave plantations and performing assassinations often enough for it to be notable. These are things that your PCs are likely to do.
Religion
These guys are not in this game
So, it starts out be telling you that zombies don't find human religions particularly appealing. In other words, no zombie catholics. Or, rather, they're rare as fuck. If you want to use a real world religion, there is Santeria and Hatian Voodoo. Otherwise, you have to worship or hate Zemi. Zombie religions are given no elaboration. They exist, and most religious zombies follow them, and we know fuck all about them otherwise.
This is an actual disgrace.
Supernaturals
Zombie is set in the World of Darkness, which means that it has to address all the other World of Darkness splats. It does this by stating that the other splats don't know that zombies exist. And also. that some upstarts are raising armies to take on the other supernatural races. This is obvious an adventure hook for Zombies vs Vampires.
There's also a sidebar that gives the differences between zombies and vampires. But they should already be apparent if you've been reading.
The Market
Makes no sense, in terms of population. The Market is zombie takeout. Instead of spending all of your time searching for homeless people to eat, you have professionals deliver them straight to your door.
Vampire needed this shit. If there was a group of vampires that made a fortune supplying blood to other vampires, it would almost make sense. But New York City has has 28 zombies living in it, most of whom are homeless and making less than minimum wage. There isn't much profit in providing meals for them.
Much like Vampire, Zombie completely ignores its own demographics, because RPG writers have no sense of scale.
Subcultures
We've got three "subcultures" of zombie. Rich Zombies, guilty zombies, and crazy zombies. There are enough rich zombies for it to be an entire subculture, somehow. Guilty and crazy ones are explicitly disfunctional, and you probably don't want to play as one. They're basically NPC material. For the Crats, which is a stupid name for rich people, we're treated to a short story about high-level business dinner meeting, in which the dinner consists of several living and conscious people who are connected to life support machines in order to keep them alive as long as possible.
Cells and Factions
This is actually more reasonable than Vampire, in terms of numbers.
There are two major factions, The Circle and the Echelons. Both lack overarching faction goals other than maintaining their own power, but that's okay. It's not like real world states have faction goals otehr than maintaining their own power.
The Circle is the Grande faction. The Echelons is the Jackal faction. Neither faction is actually racially segregated, and both will accept members of either race, but Grandes tend toward the circle, which is more Grande friendly, and the Echelons were origianlyl founded by Jackals who didn't care for the Grande dominance in the Circle.
Under the factions, you have the cells. There are 13 total, 5 for each faction and 3 independent. Overall that means 1500 zombies per cell, on average. Less when you consider independent cadres.
This isn't as bad as Vampire factions became. Where globe-spanning conspiracies have like three members because that's all the demographics support. Expansions would have made it worse, but this splat doesn't have expansions.
Each cell gets its own short story, followed by a brief description. Some of them are well thought out. Others aren't. The cell of crazy zombie body moddery who graft body parts of other supernatural creatures onto themselves are interesting. Zombie street gangs, less so.