There are various schools of thought about adding historical detail to fiction. Sometimes you want more detail, sometimes less; partly, that depends on the book’s genre. For example, in a Tom Clancy novel such as The Hunt for Red October, there is a lot–a lot–of detail about nuclear submarines. But if you’re reading that book, it’s likely that one of the reasons is because of all that lovely, crunchy technical detail.
Historical novels need historical detail. But how about historical erotica? How much historical detail does there need to be?
There should be as much historical detail as I want. And the geekier, the better.
If the details I choose to include are not what the reader expects, that’s all to the good. Those details will stick better for being unusual. (cf. the picture of a horse wearing a gas mask.) And because they stick in the reader’s mind, they’re more useful for building up a picture of the time period, and also a picture that feels deeper and richer than whatever generalized ideas the reader might have had. (What does World War One mean to you? Trenches? There was fighting in the mountains of Italy, as well. And in Africa.) I feel anything that brings the reader more completely into the story is a good thing.
The more geeky the detail, the more that detail feels specific. Specificity is important; the more specific, the more vivid and immediate the image becomes in the reader’s mind. You can say, there were birds. Or you can say, she remembered the poignant cries of bitterns and the song of reed-warblers, and the occasional slow dignified silent soaring of a heron towards the far horizon.
The more specific the detail, the less often you have to use detail, and the more subtly you can use it.