The Winter Palace tells two stories: the rise to power of the Russian Tsarina Catherine the Great; and the fictional life of a young and poor Polish girl, who grew up and gained trust as a spy in the Russian imperial court. The book is full of the intrigues, politics, deceits, illicit liaisons and treacherous shifting alliances of the court; unfortunately they are presented too narrowly from the embittered viewpoint of the servant rather than giving a broad perspective of the period or of Catherine's life.
I am being generous in giving it 4 stars. I visited an exhibition of Catherine's life several years ago and it was much more informative and made a deeper impression on me. She was a fascinating person - not called "the great" for nothing - and many people will find it worth reading a more serious book about her. However, if you are new to the subject or just want a light read about the Russian history and politics of that period, it is entertaining enough.