Let's start with the names. I'm sorry, did you say Vespa? Isn't that a kind of Italian motorbike thingy? And isn't Nyx the goddess of night? So you mean to say that we've got a protagonist whose first name is a motorbike and whose second name is a goddess?? I'm sorry, but these kinds of names are just one of my pet peeves.
While I know that lots of people will feel differently, but I actually didn't have all that much of a problem with the first and third person switching. I mean, at least this avoided us having two voices that sounded basically the same.
I didn't like the character's personalities much either. Aside from her name, Vespa just seemed stuck up, a bit mean and not very smart either. I didn't have a big problem with Syrus, except for the fact that he wasn't very easy to connect to and sometimes he was not-so-bright either.
Now onto the plot.
I liked the plot, much more than the characters. It was fast enough to keep me interested, yet not so fast I didn't get what was happening. It also had a few twists, so it was interesting enough that I overcame my general annoyance with the characters.
The setting didn't have enough explanation. So, we knew that it was set in "New London", which became New London after the original London went through a magic portal and got transported to a world where there are things like Sphinxes and stuff like that. I have a few problems/questions with this setting. Question number one: how did this magic portal come into existence? Question number two: How the heck do you get all of London through a magic portal? Question number three: Is New London the only civilisation on the whole world? If it is, why are they all crowded into a tiny city when they have the whole planet?
My only hope is that my questions will be answered in the books to come.
Despite all my problems with Unnaturalists, the world was quite a well constructed one, and I would recommend it if you tend not to be bothered by the problems I have with this book.