Though a young adult novel, Leviathan is one of the most fun books I've read in a while. Its alternate universe version of Europe on the eve of World War One imagines the major powers equipped with cool steampunk technology. The British and their allies have fantastical genetically-engineered creatures, such as living airships, on their side, while the pickelhaube-clad Germans clank about (naturally) in giant, armored walkers. Such concepts have been done in fiction before, but Westerfeld creates a thoroughly enjoyable world, filled with likable characters, drama, wit, sci-fi speculation, and some real history. It's written on a level accessible (and appropriate) to middle school-aged kids, but I think many adults will like it just as much. Can't wait for the sequel! PS. If you don't get the print version, be sure to check out the grotesquely cool map of Europe on Westerfeld's web site.