This novel kept surprising me over and over, which is impressive for the fourth book in a series, when you would think you knew what you were getting. Perhaps my favorite part where the (sometimes tricky) conversations between husband-and-wife, though the weaving in of Lord Byron was also rather fabulous.
Now, I know the next book is written, though it's not out yet -- must plot a way to get Mary Robinette to get it to me a bit early