Last night I read a blog comment in which someone claimed ey otherwise enjoys reading A Song of Ice and Fire, but are frequently thrown out of the story by too-modern word use on the part of the characters. Specific example used being the word 'fuck'.
I would be all on board with this except that:
(a) According to the sources I've checked, including the Online Etymology Dictionary, the word dates back to at least the 1500s and
(b) A Song of Ice and Fire is not actually a series of historical novels, nor even historical fantasy. It is a fantasy series set on a fictitious world with no connection to ours, and is under no obligation to be period accurate in the words used by its characters. I would say 'period accurate' is a nonsense phrase when applied to such settings, unless one is referring to a historical period within the setting.
This is, yes, a pet peeve of mine that some people seem to believe fantasy fiction set in fictitious settings is under some obligation to conform to the history of our Earth in whatever specific details they nominate. Presumably, the bits that don't have sorcerers, dragons, non-human peoples, unearthly deities, continents that never existed on this planet, political units that never existed on this planet, languages no human has ever spoken (sometimes no human could speak), or climatic arrangements that would be unbelievably improbable if not impossible in the real world. But most of the characters live under a feudal system of government and haven't discovered steam power yet, so they better not say 'fuck' when they cuss, 'cause that's unbelievable.
So long as the setting is consistent with itself, it is probably fine.
 I don't recall any, although it has been about 10 years since I last read the series.