Q: What do you get if you take the Hungry City Chronicles and remove most of the subtlety from them? 
 A: "Worldshaker." 
 Yes, Richard Harland's steampunk adventure "Worldshaker" does not manage to do much that is new, but it does a fairly decent job exploring the setting of a vast, moving country. Hs lead characters are likable and well-developed, but unfortunately the morality ends up being too black-and-white for most teen readers. 
 Col Porpentine has just been named the successor of his grandfather, who is the commander of the Worldshaker (think a portable England). He lives the elite lifestyle of the upper classes, while mute "menials" serve them, and unseen "filthies" keep the Worldshaker constantly moving. Col has lived like this all his life, and his destiny seems to be set. 
 You can guess what happens: he encounters an escaped Filthy girl named Riff, which shatters Col's comfortable worldview. As he learns more about the Worldshaker and the cruelty of the people who command it, he also finds that his sympathies are rapidly shifting to the Filthies. 
 I love futuristic steampunk adventures, and I adore the Hungry City Chronicles. But "Worldshaker" just... didn't click for me. Perhaps it's the chasm-like divide between the villains and heroes -- the villains are Evilly Evil for the sake of Evilness, while the good guys are pure of heart. No subtlety, no shades of grey. 
 But despite the familiar premise, it is a well-developed story. Harland devotes a lot of time to the social strata of the Worldshaker, and the class war that is rapidly brewing from the lower decks -- as well as how the upper classes are trained not to even see the Filthies as humans. He does do a good job of that. 
 As for Col and Riff, they are sadly the only characters given a thorough fleshing out. They're likable, but nothing special -- he's an ignorant rich boy, while she's a plucky poor girl who is trying to evade the mysterious process that turns Filthies into menials. Actually, I would have liked to see more from her perspective. 
 "Worldshaker" is... okay. It's not too original and there's little moral greyness, but it's still a light, enjoyable steampunk read.