Set in a far-future Earth where a Calamity of Physics has resulted in zones that allow different levels of technological sophistication — like Vinge's Zones of Thought but at town-sized scale — this is very nicely done. It starts off reading like a China Miéville story, where the details of how exactly the world works take a deliberate back seat to the interestingly-wacky not-quite-steampunk storyline, but by the end we're clearly back in Alastair Reynolds territory. Recommended.
ISBN 9780575088504.