One of the trickier things about historical fiction is trying to make the language, particularly the dialogue, sound like it belongs to its period while still being easy enough to read for a modern reader. For fairly recent times, this is not much of a problem. The biggest difficulty in writing a story set in the 20th century is probably dealing with words that were perfectly ordinary then and are considered slurs or otherwise offensive now. But go further back and the problem becomes more complex. Go back to the Anglo-Saxons, as I do, and it becomes quite a head scratcher.