Historical fiction centered around people who were actual people unfortunately reminds me of Real Person fan fiction which is a bit of a personal squick unless it's clear that it's alternate reality, fantasy or science fiction. In fanfic it's considered important to either keep borrowed characters IC (In Character) or to state that such characters are OOC (Out Of Character) and I would expect it to be no less important in professional writing.
Historical fiction centered around original characters reminds me of any piece of fiction located somewhere that the author can't personally check out.
I don't expect complete accuracy but an obvious lack of research is grounds for serious criticism and any readily avoidable errors are worthy of comment. The amount of research I expect depends on the genre and 'seriousness' (for lack of a better word) of the book, I don't expect accurate police terminology from a light-hearted cozy but a serious police procedural should have correct terminology.
What I don't expect from a historical novel is to be told what are known facts about day-to-day life and what are necessary extrapolation. The more serious authors tend to write author's notes giving an overview of the historical facts vs authorial extrapolation but not always.
|