Summary: Stay with me, here. Partly inspired by the inception of WWI, this book is about a sort-of heir to the throne of Austria-Hungary who goes on the run in a battle machine after his parents are assassinated, a British girl who dresses as a boy so she can pilot airships (which are actually genetically engineered monsters that fly, because in this reality, Darwin discovered bioengineering), the start of a war, and some mysterious eggs.
Verdict: What a gas-bag!
Yay!: The concept is interesting, exciting, and well-explained. A couple of the side characters are interesting. The book is nice and thick, and fast readers might appreciate its substance in that way.
Nay!: Leviathan is as bloated and lumbering as the live airship that gives the book its title (and this is coming from a fan of the author.) While the bioengineered creature premise is extremely cool, it never gets off the ground and becomes an integral part of the plot. I hope that changes in the sequel (this is the first in a series). Meanwhile, this reader was left wondering how this book wound up getting sold as YA. Apart from a few references to the heroine's breasts, the subject matter could easily work as mid-grade. The hero and heroine, who are supposed to be teenagers, have the maturity of ten- or twelve-year-olds instead. You would expect a scrappy girl from the streets and a teenage prince to be less naive, but alas. Also, can we please stop writing books about girls who dress as boys because only boys are allowed to do boy things? This is a parallel, imaginary universe. There's no reason not to have the biologically sensible Darwinists allow females to enlist in their air corps. Having Deryn dress as a boy is just a gimmick to add interest to her story, which would already be interesting enough if she weren't so darned annoying. Every other sentence out of her mouth contains either "bloody" or "barking spiders!" Get a new exclamatory phrase already! Mix it up! Where I am from, "barking spiders" is a joke elementary age boys make when they pass gas audibly. One can imagine my initial confusion about the heroine's gastric system...
In conclusion: I don't care about the plot, the characters or the series. I REALLY want to know what was in the eggs....but that's what Google is for.