Nova Swing by M John Harrison
Award-winning SF noir novel from 2006, the resolution (or lack thereof) perhaps unworthy of the set-up, but worth reading if it's one of your sub-genres of choice.
Vic Serotonin is a tour guide, leading wealthy tourists to the unstable edges of Saudade, where reality isn't as real as it could be and no-one knows what you might find. In between clients he hangs out at Liv Hula's bar with Fat Antoyne, who only wants a chance to fit in. Together they watch the cats stream past twice a day, and the ships taking off and landing in the city, largely minding their own business. Sure, Vic smuggles the odd artefact out of the event site for collectors and the mildly eccentric Detective Aschemann keeps half an eye on him, but it's not such a big deal. Until it is, and Vic really finds out who his friends aren't.
With any kind of noir it's the details that make it, and when you're weaving some sci-fi world-building in, doubly so. The details in Nova Swing really make it work. There's a musical theme which I liked, as well (playing it, listening to it, watching performers in bars).
Nova Swing is described as the sequel to Harrison's earlier novel Light, which I haven't read but I understand it to be set in the same place with completely different main characters. I didn't feel like there was a gaping hole in my understanding as a consequence, it just felt like I'd been dropped into a complete world where life went on before I started observing the place, and will continue (after a fashion) after I've gone. That should be the case with any well-written fiction, anyway.
I didn't feel completely satisfied by the time I closed the back cover, one too many loose ends perhaps. Nevertheless I'd enjoyed my time in Saudade and I was left with a dreamy feeling of enlightenment being just beyond the grasp of my sluggish brain. If you don't mind having some questions remain unanswered as long as you've absorbed the atmosphere of the place during the investigation, then this might be just the SF noir for you.