The author who attempts to create a piece of historical fiction has challenges and choices not faced by writers in other genres. Aside from the obvious of having to research the era under observation, one has to then decide about the application of the knowledge. Is it the history or the story that is most important?
Some authors choose to set a story in a different time as a means of exploring actual historical events; telling history through the eyes of a fictional character is an effective means of bringing to life important epochs in a manner that a textbook is never able to accomplish.
For others the lure of history is the appeal of the exotic locale. They utilize the atmosphere of a particular period as a backdrop for the action they have envisioned for their heroes and heroines. These "costume dramas" have less concern with historical events and more for historical mood.
In either case the major challenge of the author is the incorporation of their research into the novel without it being detrimental to the activity of storytelling. Do they get so wrapped up in displaying their knowledge that they fall short in other areas of the novel? No matter if they are giving an account of an actual battle or telling a story set in the 17th century they still need to create characters we care about and provide a storyline that interests us.
Chelsea Quinn Yarbro's latest work falls more into the area of costume drama than recreation of actual events. (A sub genre of speculative/fantasy within historical fiction) States of Grace is set in Europe of the Counter Reformation when the Catholic Church is reacting to the establishment of Protestant sects.
Where her work differs from a lot of historical fiction is that her protagonist, The Count Saint-Germain, happens to be thousands of years old and a vampire. At this point in his existence the Count has established himself as a successful merchant in Venice who also has publishing interests throughout the Lowlands. (This was the name given to roughly the territory we now know as Holland and Belgium. It was controlled primarily by Catholic Spain, but the local inhabitants were some of the first to convert to various strains of Protestantism. This area was a therefore a flashpoint for violence and abuses by both sides in the fight for souls.)