Vincent Katherinessen and Michelangelo Kusangi-Jones, a long disgraced diplomatic couple, have been dispatched to New Amazonia. Ostensibly, they are there to negotiate the return of a series of looted art treasures. Covertly, they are both there to steal the alien power source that drives New Amazonia's cities. They find themselves caught up in political infighting New Amazonian's ruling matriarchs, while also attempting to pursue their own private agendas: Vincent in support of his mother and his home world of Ur, and Angelo in reluctant opposition to his lover's plans.
Bear's world building in Carnival particularly good: humanity ruled by a ruthless set of artificial intelligences, programmed to keep humans from overwhelming their local environments via remorseless culling program; New Amazonia with its heat, humidity, living cities, and, for the unwary, dangerous jungles. Local Amazonia culture is a beautifully drawn inversion of the a traditional patriarchy, where men are kept in harems and prevented from moving freely by a licence system, where women rule and duel over matters of honour, and where the major political division is between those who support the status quo and those who favour improved rights for men. Inevitably, both the diplomats and the locals regard each other as barbarians: the Terran representatives can't believe that their hosts eat meat, while the Amazonians are appalled by their visitors' views on abortion, genetic manipulation, and homosexuality.
Despite liking the book a lot and enjoying the journey of ideas as it unfolded, I couldn't entirely reconcile myself to the ending which didn't seem to have quite enough weight to cap the plot that had preceded it. Probably my fault for enjoying the build up too much — I'm sure I'll like it more on a re-read — but it certainly wasn't to dampen my enthusiasm for the book.