I gave this 3 stars--I liked it--for story, but would bump it up a half star for good craft, although I think that enjoyment was enhanced by the fact I read the non-fiction biography Catherine the Great: Portrait of a Woman a short while ago. It helps considerably to have some background on the history and the main players. Some readers have complained that the subtitle of The Winter Palace: A Novel of Catherine the Great is misleading because the first person narrator is a courtier/spy in the court who primarily serves the Empress Elizabeth prior to Catherine's ascension to the throne. I would agree to some extent. This is fiction using a fictional character to shed some light on a historical character--a technique used by many writers (including me). The author covers over twenty years in history--a difficult task in fiction--and does it well. 
 Varvara, the fictional protagonist, is an interesting character and manages (for the most part) to carry her weight in telling the story. She can walk in more worlds than Catherine, so we get insight into the lives of servants, poor street beggars, and army officers; as well as court intrigue and the private life of the rich and powerful. From the author's note, her next book in the series will be from Catherine's POV. The author's extensive research shows in the details: clothing, food and drink, architecture, folk lore, medicine, plants, smells, etc. Sometimes the details overwhelm the story, but for the most part they provide a great background and enhance the atmosphere. Altogether, an enjoyable read, but it helps to know about the history and characters before hand.