content: This series is a masterpiece. Buy it (if you can) and set aside enough time to read it. It's worth every minute. The 'plague' referred to in a previous review is the biological mechanism that allows the human inhabitants of the planet to survive the massive temperature extremes that occur over the 'year' (1000 earth years). The temperature ranges from sub-sub arctic to ultra-tropical and the physical changes as the people go from short fat and conservative Winter people to tall thin active Summer people are described with marvellous detail.The story of the humans and their interaction with the natives of the planet is interwoven with the technical information with a masterful flair.This series is similar in breadth and vision to the Eden series by Harry Harrison, so if you enjoy one, you will love the other.