One of the best books was Medici Money, by Tim Parks, although I don't know that I've made that much overt use of it. Most of the nations of Stormwrack have individual trade treaties with other countries, though there are also economic blocs who negotiate together.
Tiladene is a collection of economic cooperatives, and some of that comes from experiences I've had with actual co-ops and arts groups. Tallon is something of a navy town, where the navy is also the government. Ualtar's economy is directed by the religious leaders who run the nation.
Ooh! And Black Diamonds; The Rise and Fall of an English Dynasty, by Catherine Bailey, had a good deal about the coal town economy of England during the Victorian era and afterward.