Summary on jackvance.com:
While in Rome, art student Chuck Musgrave is offered a job painting pictures of Positano, a picturesque town south of Naples. When Chuck arrives in Positano, strange things begin to happen. It becomes clear that not all foreigners living in Positano are there for the scenery!
Foreverness writes that the book was written during Vance’s second stay in Positano (below Napels, Italy), in 1957. [ref]
Republished as Strange People, Queer Notions, Spatterlight, 2012