I've read Scar Night... twice now, I think, and it makes much more sense the second time I've read it. I've read a lot of conflicting reviews regarding this book, and for good reason too. There is a lot, a truly massive amount of events, going on in this book, and it does make for some complicated reading. There's a massive amount of interconnected plotlines (what with Devon's vendetta against Deepgate connecting with the walking tragedy that's Carnival whose plot connects with the untempered Spine assassin that is Rachel and the last angel of his line, Dill) that aren't really resolved by the novel's end, but this a trilogy, and will hopefully begin resolved in Iron Angel (book two) and ended in God of Clocks (book 3). This book really hops all over the place, but I personally found that it kept me on my toes, even if I couldn't find all the characters in my head. I would recommend this book because it is a fantastically imagined universe and it catches the eye: a city held by chains over a pit that supposedly has no bottom? An angel in this industrial city, cooped away in a temple and basically imprisoned by overprotective, overzealous Presbyters? Another angel who kills once a month by draining the blood of mortals to sustain herself, and then who wounds herself afterwards in guilt? The Spine, the temple's military arm, made emotionless by chemistry and mindbreaking torture?
The mythology created for this series, I think, is one of its redeeming points. It's well-crafted and definitely invokes images of the Christian religion (I remember that it does so, but not specifically how) to an interested, invested reader, and becomes a key component of the overarching plot itself (it's very difficult to tell what the main plot is, because there are so many subplots that the main plot is kind of lost). It's basically about an oncoming war between Ayen, the goddess of light and life who barred the doors to heaven, and her seven cast out sons (a probable reference to the fall of Lucifer from heaven, and the number seven). Ulcis, one of Ayen's sons, is the god of chains and of Deepgate, and is worshiped by the temple, of which Dill is the last living archon, the last living descendant of Callis, Ulcis's Herald. Iril is both god and Maze, the god of Hell, who claims the unblessed blood. The Maze is made of the actual souls of those in the realm, and is said to be conscious and looking for ways to break in to our world. It's a fantastic example of a universe and a religion built from the ground up, and is probably the most fascinating and intriguing aspect of the entire series. It's rather like a family drama met steampunk met religiously overtoned apocalypse. It's very fascinating.
While we're on the subject of family drama, the most heartrending moment in the book, to me, was the revelation of Carnival's (guilty vampiric angel) origins. Her backstory was heartbreaking, and reveals much about both her character and Ulcis's (who is eventually shown to be her father). The emotional and physical torture, her attempted murder by him, and the all-but-stated gang rape give her a story that relates her to the reader, and demonstrates that she exists (or existed) outside of her image as an amoral killer.
To simplify: there is a lot of potential here, much of which appears to be wasted, but with this potential comes an exciting read. I will say that you have to approach this book with a focused, invested mind, because if you're not invested in it, it'll go over your head and you'll find yourself wondering why exactly you should care or how any of it relates to anything else or what exactly something is. There aren't a lot of answers, but there's also two more books. To me, it seems to boil down to a matter of taste. Still recommended.