Indeed, Justin, I agree. What you call 'history lessons' can be off-putting even when well integrated; although in this case I was thinking less of bulky 'lessons' and more of the peppering of the text with minor bits of information which the reader may find somewhat less thrilling than the writer.

As per Rosemary Sutcliff in the following comment:
”The other terrible temptation,” she adds, ”is to try and use everything you’ve found out in the research. That can be absolutely fatal, because you really only need to use about a tenth. It’s rather like an iceberg . . . It has to be there, because it gives you the freedom of the period. But you don’t use it.”
[quote=""Justin Swanton""]What they want is a good story with a well (and authentically) textured background and believable characters, full of the ignorance, prejudices, priorities and values of their time.[/quote]
That's precisely why writing with only superficial 'stereotyped' world building often irritates me, although, of course, I do acknowledge that it depends on the context. (I perhaps should qualify, too, that when I complained about 'period stereotypes', I meant our modern stereotypes of the period, not theirs, which as you point out are extremely important in creating a sense of their world.)