I'm gonna start this review off with a disclaimer: The concepts of Armageddon and rapture are those things that are sort of a theological black sheep. Some people believe in them, others don't, and anything involving a biblical apocalypse is somewhat of a touchy subject in between most any sects of Christian faith, and certainly between other faiths. As such, a lot of people will find a lot of things in this book, at the least, very politically incorrect. As such, I will limit my review primarily to mechanical and mundane setting critiques (and my traditional digital art griping, but that's me).
I like this book. It feels very much like a theological sci-fi horror, so it achieves everything it sets out to.
Starting off, let's look at the horror stuff. I'm not much of a horror guy, so it's a little beyond my comfort limit, but it's definitely very in tune with Christian theology and the sort of bad things that happen there.
Science-fiction wise, it's pretty hard with the exception of FTL (which good attempts are made to explain with theoretical methods, so it gets a couple points, even though it's a big theoretical) and a couple of things intended to build up a sense of demon-based intervention. I'm gonna take a moment here to point out what I view as a potential inconsistency involving demons here: the game acknowledges evolution as a mechanism created by God, but then disavows disease (and mental disorders too, but that's the thing everyone would attribute to a possession) as a thing of evil spirits (which admittedly transfer from host to host and involve bacterial/viral vectors), which can seem a little inconsistent at first (though it's actually not, but comes really close to being). A note to make is that they do carefully delineate that this is for their setting only, and shouldn't lead to people getting exorcisms for the common cold.
The mechanics are simple, but very, very quick, lending more of a hand to a storytelling format. I actually found that a lot of it made good sense, though I question some of the stats in the Gamemaster's section (there's an emphasis on one demon being weak to fire, which I could see, but the first thing every player will do is kill everything that isn't emitting flames with fire, so it's potentially a poor gameplay decision). Characters are similarly quick to make. Another thing to note about the rules is that for relatively simple character creation a rather different character can be created.
The system for "Extras" is one of the most interesting ways I've seen to reward players for followers while making them both incredibly useful and expendable. It also serves as a buffer for the game's very high (potentially, killer GM'ing is endorsed to such an extent as it benefits the plot, putting it in the upper acceptable bracket of aggression encouragement) mortality rate.
Ok, art gripes. I actually like the art in this a lot. It feels sort of sci-fi grungy apocalypse doom candy shiny fun dark to me, if I were to suddenly lose half of my vocabulary. The cover art is probably enough to show what I mean, a sort of hypersaturated super-dark thing I can only describe in terms that make no sense to anyone but me. I will say this though, it averts my normal "just a lot of photoshop filters over a normal image" gripe, despite the fact that that is what I believe it to be, because it actually feels good and useful. As a minor typesetting gripe, the columns of text don't quite line up, causing my obsessive side to shine through. However, it does a good job of not hurting one's eyes. At one or two parts, I saw some art that didn't fade smoothly into the background, but that's another one of my pet peeves that most people don't seem to care about.
There are also a few homophone/similar spelling word misuse errors, and a few punctuation and grammatical issues, but by the time I get to nit-picking about art and grammar, that means I've run out of actual gripes (which, you will notice, none of were directed towards the system, which is a badge of honor since I can usually find something to dislike). Seriously, though, angels are good, angles are the sort of thing you worry about when building stuff.
I guess if I had to gripe about one part of the system, it would be that the damage dice that are rolled are six-sided, while all other dice are ten-sided. That's how solid the system is (though it is minimalistic and simple, that's not always a bad thing).
Given that all my gripes had to do with the un-political correctness (which I'm not terribly up in arms about), and art/typesetting/grammar gripes, since the setting is well-thought through and has a strong connection to its subject matter, I'll give it a five for making me think, and generally being a fun, enjoyable read when I wasn't nit-picking. Also, the game does a good job of mixing various cultural, religious and political ideologies, even though the strength is primarily in political and cultural ideologies, since the religious focus is entirely Judeo-Christian (and, ostensibly, Muslim, though I didn't see much evidence for that and I wouldn't if there was). That said, it might be hard to find a group willing to play this (at least if you go into all the gory details all at once, if you ease in it may be more tolerable, but reading all the game in one sitting would be a major speed bump for some groups). Also, the price could be an issue, but with the amount of content (maps and an interactive character sheet that can be printed) that comes bundled with it, Rapture: The End of Days shows much more value than some other products.
[5 of 5 Stars!]