City of Masks is a swashbuckling adventure in a setting reminiscent of Shakespeare's Italy (complete with twins).
In the city-state of Bonvidaeo, by custom and law everyone must wear a mask and act in character with it, or face civil, social and religious penalties.
Gregorius Bass is sent to Bonvidaeo as the Envoy of Calaria, primarily to get him out from underfoot. Masked as the Innocent Man, and in the company of his radical young Bonvidaoan servant, Bass stumbles into mystery, intrigue, heresy and murder.
It's speculative fiction (though it's neither science fiction nor fantasy). It's a mystery (with a serial killer) and an adventure (with a sword fight after a rooftop chase). There's intrigue, some humour and a little romance. Beneath it all, though, is a serious reflective point about identity and social convention.