I think the reason I love vampire and werewolf stories so much is how old the legends are, and how much they share while still having unique cultural and regional differences. I love when people play with the hows and whys of vampiredom. I might even have been okay with sparkling if it had been more subtle and had some sort of pseudo-science attached to it. Of course, nothing could have saved that other series from bad writing, so we'll just move on.
In this particular series, vampires and werewolves and ghosts exist, or rather are able to exist, because they have an excess of soul. This happens to be a world in which dualities exist, so because there are people with an excess of soul, there are also people with no soul. These are called preternaturals, and any supernatural that comes into contact with one returns to their mortal state as long as the contact is maintained. These people are strangely presented as having no innate sense of morality, so technically they would be more dangerous than werewolves or vampires, the latter being able to find willing victims now that society knows about them.
Since preternaturals are extremely rare in Carriger's world, the only one we have to judge is Alexis Tarabotti and to some degree her deceased, but frequently mentioned, father. Tarabotti is presented as overly strong willed (meaning she has any will at all in Victorian England) and somewhat socially crass. I think I would have liked to have seen her be more so, and perhaps evincing signs of Asperger's. I mean, it would be an interesting correlation, not that I think people with Asperger's lack souls, but there might be some correlation of soulless behavior with a lack of empathy, etc. Then again, I'm not certain why Carriger didn't go the psychopath route either. In any case, Tarabotti apparently reads a whole bunch on philosophy and moral development and this somehow solves the problem of her having no built-in moral center.
Ah, another thing about the mythos of Carriger's world that I found interesting were the social dynamics of the supernatural creatures. Werewolves are apparently the more social of the creatures and have lent England's military their social order. While they're supposedly immortal (or at least long lived), they tend to fight each other, so they don't live nearly as long as vampires. Vampires tend to live in hives, with a queen being dominant. Werewolves also place Alpha Females above Alpha Males, but since there are so few of them it hardly seems worth mentioning except that, once again, this is almost hilariously indecorous for Victorian times. Both supernatural groups tend to shun outsiders, although werewolves more so. Lone vampires are seen as kind of eccentric, but can apparently gain some status if they're old enough and not too crazy.
In any case, I love new social dynamics and the new stuff made this an interesting read. Carriger seems to have a good understanding of how much is too much to throw at her readers all at once, and none of the plot or character got derailed or detracted by it. I was even pleased with the touch of smuttiness in the book, and while we don't see any premarital sex scenes, this is more due to individual decision by the characters rather than blatant abstinence only Mormon driven drivel.
For something slightly related, the New York Public Library staged a fabulous event where Improv Now stormed the building in ghost and Ghost Buster costumes to the obvious enjoyment of their patrons. More here.