Yes! I haz it at last!
“Goliath” is the final book in Scott Westerfeld’s young adult steampunk trilogy (I reviewed the other two here). Since it’s set in the early days of World War One (a very alternate reality, in which “Clanker” technology – all metal and gears – is pitted against “Darwinist” technology – genetically altered beasts including the enormous flying airship “Leviathan”), it’s technically dieselpunk.
The rest of this review has been moved to Comfy Chair, where I get paid for it.