Ambien II is one of The Five, the highest level of the Sirian Colonial Service, who have been the hidden rulers of Sirius for many thousands of year. She is a competent, skilled administrator and manipulator of populations and events - in essence a bureaucrat, but according to the demands of the Sirian Empire, for she is always and everywhere first of all a Sirian official, though she does try to temper severity with compassion and believes herself to be something of a liberal.
The Sirian Empire thinks very well of itself, imagines itself the crown of the Galaxy, despises the Canopean Empire, seeing it as a rival. In reality, Canopus is in advance of Sirius in every way, is in fact ruler of the Galaxy. Canopus, having defeated Sirius in war, behaved magnanimously, and thereafter has been trying to life Sirius to its own level, but in subtle and long-term ways. Ambien II is the individual whom Canopus uses to introduce higher and nobler ideas to the Sirian Empire. She has no inkling of this - not for long ages. But slowly she comes to see how much there is to learn from Canopus.
This book is an account, from the point of view of Ambien II, of her growth into an understanding of the comparative barbarity of Sirius, of her own barbarousness and crudity - the beginnings of her comprehension of how great and marvelous a creation the Canopean Empire is. She is writing an account of the relations of Canopus and Sirius that contradicts that of the official historians, and this act is part of a power struggle that is convulsing the Sirian Empire and will transform it.
The Sirian Experiments is the third book in Doris Lessings sequence Canopus in Argos: Archives, which she began in Shikasta and continued in The Marriages Between Zones Three, Four, and Five. But her space age saga is in no sense merely a record of celestial events but more a form in which we may dare to face the consequences of our own actions and the destiny to which we are being drawn.