I've been speaking a lot on historical novels this week, and the question always comes up: how does the reader tell what's true and what isn't? It seems that the avid reader gobbles up book after book, and in the end may not consider much whether the author has a bias, wants to influence his audience's thinking, or just skews things to make a good story.
I think authors should clarify somewhere, in the foreword or the afterword e.g., what is true and what isn't in a book. History isn't truth, but novels need to bend truth even more, so it's only fair to give a more truthful version for the interested reader. Those who just want the story can skip it, and those who want "truth" have their chance.