I'm going to have to disagree with some of my fellow commentators; if you approach the book with a great deal of historical Russia knowledge, perhaps this will seem shallow to you. But the book is called "CATHERINE the Great," not "RUSSIA the Great," and I think it provided a perfect amount of context needed to understand Catherine, her reign and her court. Additionally, while rumors and anecdotes ARE mentioned, they are not cited as authentic; it is made quite plain and transparent that what is being relayed to the reader IS a rumor or an anecdote, sometimes even multiple explanations for the same event are given with the disclaimer that the truth is not definitively known.
If you like historical fiction but generally shy away from historical non-fiction, this is an excellent crossover/gateway book. While it is a lengthy volume, it never gets droll or feels like you're reading a textbook; Massie tells a story, and doesn't just relay academic research and facts. I found it fascinating.