Scott Westerfeld is an awesome writer.
I really enjoyed the Uglies series.
I read those and then plowed into Leviathan and Behemoth, both excellent books. I can't wait for Goliath to come out. I just really enjoy his style. His books are super creative and have excellent world building.
They are the kind of books I try to learn from but get so lost in the story I have a hard time figuring out how he made everything so intriguing because I'm so into the plot.
I highly recommend him if you like YA sci-fi or steam punk.