Cetaganda (Vorkosigan Saga)
In the Vorkosigan Saga, which is part of the greater "Bujoldiverse" which includes "Falling Free", there are at least four different human cultures which take genetic engineering to a high level. The low-gravity-dwelling "Quaddies" of Falling Free are the creation of a spacefaring culture which is still largely Earth-based, and no sooner have low-gravity humans been created than someone invents artificial gravity fields which makes them obsolete. That is in the distant past as far as the Vorkosigan saga is concerned, though a Quaddie musician does appear in one of the tales.
Beta colony has advanced genetic manipulation, mainly employed, it seems, to create a new gender for Betans to be sexually permissive about, and genetic engineering of the most dubious kind is a monopoly held by one of the vilest criminal houses of Jackson's Whole. In those cases, genetic engineering and all its products merely reflect the nature of those societies. Cetaganda, however, which in most of the Saga is seen simply as a militaristic and aggressive galactic empire, turns out to be a genetic project of the highest order. The empire is ruled by the "Haut" who are busy designing themselves, and not just their underlings, to better rule and colonise ever more of the galaxy.
For Barrayar, the home planet of the Vorkosigan family, its time of galactic isolation and technological backwardness ended with the bang of a Cetaganda invasion (by Cetaganda's "Ghem" warlord and artist class), brutal occupation, and bitter war of independence, during which enough Cetagandan nuclear weapons were used to make large tracts of land uninhabitable and for mutations to be a real problem and a social horror. Cetaganda is not only the defeated oppressor, but its culture is based on altering human form and nature, which most Barrayans would recoil from.
On the death of the Cetagandan Dowager Empress, who turns out to be much more important than outlanders ever knew, the Barrayan Emperor Gregor sends Miles Vorkosigan, his foster-brother, and Ivan Vorpatril, their mutual cousin, to represent him at the inevitable state funeral. It has only been a couple of years since Miles discovered a Cetagandan plot to invade a colony, Vervain, which was then thwarted by a Barrayan fleet commanded by his father. His grandfather having led the army which expelled the Cetagandan occupiers from Barrayar itself. There couldn't be a more diplomatically sensitive occasion, nor a more sensitive diplomat.
Within seconds of docking at an orbital station over the Cetaganda capital, Eta Ceta, Miles and Ivan are embroiled in a dangerous plot to overthrow the current Cetagandan Emperor and, indeed, change the whole direction of planned development for Cetagandan society, which will make it even more of a threat to Barrayar in the long term. Assuming that the plotters don't succeed in using Miles as a pretext for a more immediate war with Barrayar.
What follows is the usual ripping yarn of Miles Vorkosigan winging it through high politics and low violence by luck and instinct, with Ivan, informed by a dangerous childhood growing up with Miles, trying to stay out of the political trouble which Miles attracts and get himself as deep as possible into the sort of trouble represented by numerous lovely Ghem ladies. What is unusual, for this saga, is the intricacy of the world imagined and described, and the complexity and galactic importance of the plots and undercurrents which Miles encounters, and, with typical foolhardiness, attempts to manipulate in what he perceives to be the best interests of Barrayar and Vervain. (It takes but a single meeting with a female anthropologist, twice their age, from Vervain,to have Miles and Ivan seeing Vervain's interests as being just as important as Barrayar's.)
And the ruling Haut ladies, when Miles finally sees one (something hardly any outlander ever does), turn out to be even more compelling than Ivan's hareem of willing Ghem ladies.
Along the way, it is apparent that the Cetagandan fashion for Ghem lords and ladies to compete for the attention of the Haut by engaging in competitive genetic engineering for purely artistic effect, is capable of creating both exquisite beauty and abominations in Barrayan eyes to rival any horror made on Jackson's Whole for the amusement of its crime lords and their clients. A kitten tree, for example.
As ever, the Vorkosigans and the Vor class in general, appear to have walked out of one of Tamara De Lempicka's portrait's of Czarist Russian military aristocracy, but this is really about their Cetagandan counterparts, whom Miles ought to hate, and doesn't.
There's an imaginative vision of a very different human culture here, not just as Cetaganda stands at the time of the novel, but as it's meant by the Haut to become, and the intriguing possibility that Cetaganda may be more important for the long-term future of the Bujoldiverse than Barrayar and the Vorkosigans.