Not totally accurate--because let's face it, not many books are. And I don't mind some anachronisms. However, I dislike historical romances where the setting is merely that: setting. Like little kids playing dress-up, the characters could be anywhere--the rules and problems and expectations of THIS society don't matter.One of the hardest aspects of historical plausibility for M/M authors isn't the difficulty of acknowledging that gay men had a difficult time in the past. The difficulty is in acknowledging the historical viewpoint that even the gay men likely held.
Consequently, I greatly admire those authors that tackle the actual viewpoints of the time period without (1) translating those viewpoints into acceptable twenty-first versions; (2) apologizing for them.
I will be reviewing Jackie North's books later but right now I have to mention how impressed I was by her Wild West time travel books. When several modern characters attempt to "correct" the politically incorrect speech of others in the past, the response isn't laughter or scorn or, even, bigotry. The response is that the historical characters think the MODERN characters are being rude: using terms that confuse and upset people rather than addressing them respectfully.
Regarding more embedded viewpoints, I've written about Beecroft's Reluctant Berserker.
I must also mention Katherine Marlowe's books. Katherine Marlowe takes a very different approach than the ones listed above. Although the books are Regency era and the male characters must be careful and highly discrete in their relationships, her end-of-the-novel notes challenge many modern-day assumptions about the past. Nobody in the Regency Era thought much of men sleeping in the same bed. And some of the fiercest moral arguments against homosexuality--though extant and ongoing--were not so fevered as they are today (they got especially fevered post-World War II).
Sometimes, we moderns get so convinced that history works as an arrow (all in one direction), we forget that issues rise and fall. Abortion, for example, was criminal in the nineteenth century but the argument that abortion was killing the equivalent of a sentient being didn't have the emotional impact then that it does 100 years later.
Contrary to the modern (and very Victorian) attitude that WE are the determiners of ALL standards from the beginning of time; therefore, everything that has ever happened, happens in relationship to US...
The fact is, other ages ....
Well, other ages believed exactly the same about THEIR time periods.
Good writers recognize this.