The Trade of Queens is the sixth and supposedly concluding book in the Merchant Princes series. If you haven't read the earlier books, this one will confuse the hell out of you, regardless of all the efforts to update people on the plot. I found those little summaries of what has happened so far useful to keep up and I've read the other five novels, just not in a short span of time.
Essentially it's a very well thought-out, highly realistic story of alternate worlds whose events and conflicts hinge largely upon differences in economics, politics, social customs, and concepts of law. That sounds dry, but the story isn't--it moves at breakneck speed, with a large cast of characters. Stross does a really nice job of delineating the differences a subtly different America circa 2003, the Norse colonized Gruinmarkt of the world-walking Clan, and the world of New Britain.
I'm particularly impressed at how smoothly Stross moves through complicated nomenclature and jargon within various subcultures. It's a fun series and this is a decent novel, but as my comment above might suggest, Stross has SO many balls up in the air at this point, so many plotlines going on multiple worlds, that this actually feels a bit rushed and doesn't feel that much like the series has ended. By the standards of some of the earlier cliffhangers in the series, this one wraps up, but there's still so much left to be decided.
I also feel the book suffers from Stross resolving too many of the conflicts that he poses too quickly; there isn't enough time for the tension to really build in many cases. The series is still well worth a read, in my view, and if you do you'll eventually want to know how some of the major plotlines pan out, which is the goal of this novel.