I finished Scott Westerfeld's 'Leviathan' Trilogy recently. It was pretty good.
The trilogy is set in an alternate history where World Ware One split actually rather neatly along the lines between the 'Clankers', who use technology we'd recognize as rather steampunk -- and quite advanced for the time, frankly -- and the 'Darwinists', who make use of Charles Darwin's discovery of DNA to mold living creatures into forms they can use. It's a handy technique used to cleanly delineate the 'good guys' and the 'bad guys'. However, the story follows two kids from opposite sides of the war -- an Austrian prince named Alek, and a British airman named Deryn Sharp.
But this is (supposed to be) a conglomerate mini-review.
I can't speak properly to Leviathan, as it's been a fair while since I've read it. The cliff notes is that Alek's parents were killed, so he goes on the run and ends up in the Swiss Alps. Deryn (who's disguised herself as a boy so she could join the Air Force) and her ship end up there too, too badly damaged to escape on their own. They join forces, something that's presented as fairly odd in this book.
Behemoth takes us to Istanbul, which is rather blended compared to Europe. Though rather Clanker under German influence, their designs are heavily animal-inspired, and there's some minor indication that they use animals too. Alek and Deyrn assist a local revolution in order to prevent the war from ending unfavorably. There's lightning cannons and creative improvised weaponry, and apparently Deyrn's been in love with Alek and I missed it. Good book.
Goliath is probably the weakest of the bunch. It ties together a decent number of threads from the other books, and its tour of the Americas shows us that Clanker and Darwinist can get along. But its major plot, while well-written, seems rather cheesy, almost to the point of Deus Ex Machina (well, sortof -- God is the Machine, in the sense that the Machine doctor Tesla calls Goliath is supposedly going to end the war; but God has the machine, as Tesla has something of a god complex), compared to the other books. Still decent, just not as good. I wasn't fond of the way the core conflict was wrapped up.
Pass on Leviathan
Eight of Ten for Behemoth
Five of Ten for Goliath
Seven of Ten overall.