Jandys asked "Does anyone know of a database source that lists books by the location of their settings?"
After some poking around, I came up with We Tell Stories and Place Studies. Shree left a comment that suggested The Hieroglyphic Streets and Bookpaths
But the consensus seems to be a resounding "No". Which got me thinking that perhaps this is something I'll have to do myself. Something like a Google Maps Mash-up meets IMDB (IBDB and IBookDB are already taken, btw). Who wants to help?