On any voyage there is always a danger of culture shock, time travel being no different from any other passage amongst foreign peoples in this regard. It requires a great deal of commitment to fully comprehend a foreign culture. For the uninitiated the differences seem overwhelming. Accumulating enough knowledge of context to even begin to understand it all is a tremendous undertaking. Many people are daunted by the idea of pledging themselves to such a large task and they are unwilling to travel alone —but they will make the journey, with all its rewards and adventures, if they may do so in the company of a kind guide who can explain what they are experiencing. If reading a primary source from a different era is like journeying alone to a foreign land, then reading well-written historical fiction is like travelling under the guidance of a knowledgeable companion.
The best guides in travel are the ones who show a culture as it really is, not just as they suppose their guests will want to see it. A tour guide in Europe who only showed her American visitors small communities of American expatriates would be deficient at her task: an author who only uses historical settings as a way to make thinly-veiled social commentary on current topics is an equal failure. However, denying that connections and parallels exist is likewise detrimental to understanding. It would be ridiculous for a guide to race ahead of her visitors covering up foreign products or hiding immigrants in closets so she could give travellers a "real" view of her homeland. Connections and shared ideas do exist between times just as they exist between places; a skilled guide will bring her visitors into situations where they can witness these parallels and draw their own conclusions.
The most skillful guides help at interpretation, but at the same time manage to be unobtrusive. A tour guide who carries around an encyclopedia and stops at every streetcorner to read out long, verbatim passages would rightfully be considered a bore. Similarly, I find it very tiresome when an author continually halts their narrative to expound on non sequiturs which do not build their characters or move their story forwards. On a related topic, perpetually calling attention to things which would be mundane for a story's characters insults the readers' intelligence. For example, it is not necessary to call every lamp an oil lamp when writing about a time when electric lights were the rare exception. For inhabitants of the time in question, an oil lamp was just a lamp, and readers understand this. Insistently specifying oil lamp every time one of them is mentioned is a bit like a Spanish tour guide pointing at every pedestrian on a street in Madrid and telling visitors, "He's a Spaniard! So's he! And she's Spanish, too!…" Most of us are smart enough to work out such obvious things on our own.
More complicated elements of cultures (past and present) do require interpretation to be comprehensible to visitors, and serving that function is one of the tasks of an author. There is a skill to weaving explanation with narrative. Readers of historical fiction come to the genre because they want to learn something about the past, but at the same time, they want a story —if they didn't, they might as well go for that encyclopedia. It is the job of a writer to satisfy both of these desires. I started my historical fiction series with the tale of the first bicycle in Chetzemoka because I knew that a high-wheel bicycle would be a foreign object to many readers. Since it was also a new piece of technology to the residents of the town I'd created, there was a legitimate reason for explaining its details in the context of the story.
If a fact is interesting and pertinent enough to be included but would detract from the story rather than adding to it, then its proper place is in the book's appendix. One of the most memorable tours I've ever taken was of Edinburgh back when I was in college, and was led by a grizzled Scotsman who worked for the hostel where I spent a few days. About halfway through the tour the feud between the Campbells and the MacDonalds came up as a subject; our guide had very strong opinions about that feud, but he told us it was a story for the highlands, not for Edinburgh. It wouldn't be part of the tour but anyone who wanted to hear it should join him in a pub after he'd finished showing us the city and he'd tell us the tale over his pint of Guinness. A book's appendix is a bit like that old pub visit after my tour of Edinburgh: something fascinating and not to be missed, which relates to the story but is still not quite of the story, and is best enjoyed in its own separate space.
At the end of every trip comes the return home: fond friends embrace the traveler while begging to hear of the voyage, souvenirs are displayed with pride, and the explorer dreams of returning again to those fascinating foreign lands. There comes a point in the reading of any volume when there are no more pages to turn and it is time to put the book away—for a while. But we've brought back souvenirs from the past in the forms of memories, and the stories we tell our friends of beloved books are just as vibrant as those from physical travel. We will return again to those far off times where the pages bring us, and if we're lucky our friends will buy their own tickets and join us on the journey.