All books contain fiction. Writers, like all people, have bias. I enjoyed Team of Rivals, but I noticed Goodwin did not show much criticism. Show me her in-depth analysis about Lincoln signing off on the Scorched Earth Policy; show me where she mentions it. You may call it a sin of omission, but it does evade a truth. Matthiessen does not claim to know the truth in Shadow Country; he shows multiple perspectives about a historical incident. Many Historical fiction authors do vast amounts of research, but they can leave out hard to understand quotes. Language changes over time and Non-Fiction authors use hard to interpret source material. Some say Shakespeare did not write Shakespeare; history often hides the truth. Popular history tends to differ from accurate history.
Fiction writers use creative license to make a better story. A true historian does not get the luxury. Anything more than a century old will have holes and the Historical Fiction writer admits to filling in holes. Non-Fiction writers may just try to hide their tracks. The Scorched Earth Policy helped win the war, but it holds controversy and is ripe for condemnation. Before you blow off Historical Fiction; face some facts about Non- Fiction.