In this alternate history series Mars and Venus were terraformed a long time ago and "seeded" with Earth life, including several different human species.
After describing how people in those places survive the loss of 600 years of technological progress, the primary focus of this series turns to a conflict between a Portland-based neo-feudal dictatorship created by a sociopathic history professor, and the free communities of the Willamette Valley, most notably the Wiccan Clan Mackenzie and a group led by a former Marine, the Bearkillers.
A third series, set a generation later, chronicles the adventures of Órlaith Mackenzie, the daughter of the High King and an attack from a reborn Empire of Korea in the Californian colonies of Montival.
The series was intended as a trilogy, but expanded into five books that chronicle Orlaith's adventures to find the Grass Cutting Sword before the forces of Montival go overseas to battle the evil of the Empire of Korea.
The Draka novels postulate a dystopian slave-holding militaristic African empire founded by British Loyalists who escaped to South Africa after the American Revolution rather than to Canada (as in our history).
Stirling provides a timeline for its historical development through the 19th and 20th centuries, first as the Crown Colony of Drakia (for Francis Drake), gradually breaking away from British control to become the Dominion, then the Domination, of the Draka.
The Draka culture is remarkable for combining a strictly race- and class-based hierarchical society with near-complete gender-equality (including female soldiers in integrated military units in combat roles).
But there are never enough Draka (only 30 million or so at the start of World War II) to go around, and the bulk of the Domination's Armed Forces are made up of "Janissary" Legions recruited from the Serf population.
[6] Stirling responded to these accusations in his novel Conquistador, which contained the quotation (variously attributed to Larry Niven or Robert A. Heinlein) "There is a technical term for someone who confuses the opinions of a character in a book with those of the author.
The central theme of this series is the attempt to reunite a fragmented empire by an ancient and hidden colony-world military computer that survived the collapse of space travel and general loss of technology in society.
The Falkenberg books are part of the larger "CoDominium" series, which also includes The Mote in God's Eye and The Gripping Hand by Pournelle and Larry Niven.