When Soviet probes discovered life on Venus in 1962, everything changed - we were no longer along in the universe. With only minor differences in gravity and air composition, Venus was home to Earth-like flora and fauna, including dinosaurs and at least two humanoid races - H. Sapiens and H. Neanderthalensis. These similarities are far closer than evolution would account for, and are the subject of much research by the US base; an uneasy Soviet/American truce exists on Venus and on Earth, but the USSR keeps its work secret, and its base is miles away.
When Cajun ranger Lieutenant Marc Vitrac welcomes a new shipload of colonists it's 26 years later; Marc's been on planet a year, and is well accustomed to Venusian life. When the US forces are asked to help rescue the crew of a crashed Soviet shuttle, Marc is tapped to join the crew, along with newcomers Cynthia Whitlock (an African-American geologist with paleontology and information system skills) and supercilious Brit Christopher Blair (who, like Vitrac, has specialties in ethnology, linguistics and power systems, and flies lighter-than-air craft), Soviet scientist Jadviga Binkis (wife of the USSR shuttle commander) and Captain Tyler. After a couple of incidents the airship is unrecoverable and the team must decide whether to continue the rescue attempt or head home, but their choice is reduced to no choice when they stumble on a battle between the inhuman and inhumane Neanderthal-like natives and the far more human Cloud People.
The Sky People is shallower and less compelling than Stirling's Change series, and less engaging than Conquistador - the characters seemed less fully fleshed out, the villain was too obvious from the outset, and the scientific interest in this parallel world development was insubstantial. There was a secondary plot about a masterless monitoring AI that I found more irritating than useful, and which seemed to serve primarily as the launch pad for a sequel. The world building was intriguing, and I'd not be averse to reading another novel set in this universe, but this is far from my favourite of Stirling's work - Alex