Shadows of Umberto could be thought of as a city sourcebook, but there's enough detail here to turn it into a full campaign setting. Right away, I notice that it has a different layout and design than Joe Banner's previous module, the Green Scar. The maps are now in colour and the pdf has a wider 2-page spread. I'm not sure if this is more useful, because when I print it off now I feel like I need to bend all of the pages in half to make it a proper booklet.
"Shadows of Umberto" feels like Conan meets Arabian Tales, or sword & sorcery meets romantic political intrigue. It is divided into three sections, the first ("Shadows") details the brief history of the city and provides you with plenty of hooks and hazards to introduce to your players, the second ("Darkness") covers a very comprehensive detailing of local threats and monsters along with some choice encounters which have fictional triggers but could almost be used as random events as well, and the final section ("Dawn") introduces some custom moves for navigating Umberto along with some memorable NPCs that could be hired by the players. There is a wealth of details packed into a small space and I think I would find myself having a hard time using all of it.
My only real complaint about "Shadows of Umberto" is that it's too short. Yes, there's a lot of good information here and none of it seems unnecessary or unusable, but somehow it leaves me wanting more. I really like the simple layout of the pdf, but I feel like the 2-pages-on-1-page format of the pdf is best for reading from a tablet or laptop, and I would like to see something that is convenient for printing too. Again I'm stymied by a technical issue, but I am a picky bastard when it comes to this stuff.
You can purchase the pdf of "Shadows of Umberto" at DriveThruRPG