Leviathan by Scott Westerfeld
Basically this is an alternate history of WWI steampunk style. The fighting countries either have giant robotic mech type machines or monstrous biologically engineered animal amalgams. The main character is the "heir" to the Austro-Hungarian throne Prince Aleksander. He is a really cute character who starts off the book fighting out battles with toy soldiers and various other objects.
One of the best parts of this book are the various images which are included throughout. The pictures are very well drawn, and definitely add a certain amount of flavor and flair to the novel.
Aleksander is a bit imperious although it is entirely within character since he is a prince. Through the imperiousness though you get a sense of a child trying very hard to cope with a changing reality. There are times when you want to yell "NO!! Don't do that," but at the same time you feel as if it's only human that he should.
I would say this is mostly a read for a young adult, but can still be enjoyable for adult. The next book - Behemoth - just came out.