(Leviathan Series #2 and #3)
Fiction by Scott Westerfeld
These are the sequels to Leviathan, which I read a little while ago. It's a sort of science-fiction/historical-fiction mixture, about World War One in an imagined alternate universe.
The story was definitely interesting, but you have to stretch your willing suspension of disbelief a bit in order to enjoy it. I don't have a problem with the wildly fantastical myself (as long as the author stays within the rules of his own fantasy), so I liked the books.