Harry Turtledove 
Between the Rivers 

Young Sharur is the scion of a merchant family in the city o Gibil, loyal – he thinks – to his city’s god, Engibil, and to that god’s human deputies. But like his fellows in Gibil, Sharur is less interested in gods than in invention and trade. Then, on a routine trading expedition, he learns that the gods of the other cities, resentful of Engibil’s relaxed attitude toward his people, are uniting to punish Gibil and squelch the growing power of human creativity, epitomised by the city-state’s easygoing ways. Now only Sharur’s wits can save the city from the aroused divinities…and he’s going to need all the inventiveness he can muster.