I finished reading Leviathan, and I must admit, I am not disappointed. It was a great and engaging book, and once I picked it up I couldn't stop reading. First of all, the way it switched between Aleksander and Deryn was wonderful. It would pull you into the story of one of the characters, but once the story got extremely interesting for that character, they switched the focus to the other character. Essentially, it would leave you wanting more with a cliff hanger. I do know that some people might not enjoy something that follows that kind of style, but to me, it was quite enjoyable. In my opinion, the story focused more on the struggle of Deryn. Although I do enjoy her story quite a bit more than Aleksander's, I feel that he was underrepresented in the story and needs more character development. If the time and effort was put towards his development, I believe that I would come to like Aleksander's character just as much as Deryn's. But, his character may earn the development it has been lacking in the next book in the series, Behemoth.