My first thought on writing about the historical book was to do a video to discuss it. That's faster and easier except it sure wasn't on this topic. I kept thinking of things I should have included and simply put-- only words would do it.
There are three general types of historical books. The non-fiction is pretty obvious. It's a book that depicts, a person, event, time in history and sticks to what actually happened as much as possible. Researchers count on these books to write their fiction.
The reality is non-fiction is not always accurate nor true to what happened. They say history is written by the survivors. Well it's rewritten by their descendents. I can think of some early Oregon history books that totally misstate what happened in terms of what latter books claim. History is often written to suit a mythology or a people's idea of themselves. So even the history book has to be looked at with some skepticism and compared to other 'known' facts.
Then there is the historical novel. It takes those basic facts and adds some fictional characters or imagines conversations that the writer cannot possibly know to create a novel which has form and meter to it that life doesn't always provide. It has more responsibility though to stick to known facts but given that known facts often change, it still has a lot of latitude but more requirements if it is to be respected by readers who are as knowledgeable about the period as the writer.
Finally comes the historical romance or western which some readers and even writers confuse with an historical novel but there are differences. Any romance is first the story of two people who fall in love, their relationship, their travails and joys. To set this story into history requires a knowledge of history at least to some degree, but it's not the most important part of the story.
Same is true of the historical western like say Louis L'Amour wrote. He set his stories into a period of history and a place but the stories themselves are predominately adventures with maybe a romance thrown in.
So where it comes to the historical part of these stories, it has to be kept in perspective for what matters enough to include, what can be distorted for the purposes of a good story, and what will infuriate a reader enough for them to leave the book if it's not gotten right.
More on the subject coming up.