Never give a monkey a typewriter

You have a fiction writer trying his hand at history - always a bad idea. Then you have a mass market reviewer trying to understand the fiction writer's nonfiction and coming up with excess upon excess:
The Civil War’s Most Chicken General

"Though McClellan often seemed to be afraid of his own shadow, he could also be wildly self-assured, and The Road to Antietam captures him in all of his megalomaniacal glory."

"It’s self-regard so grandiose it verges on treason."

"“McClellan was living in a military and political fantasy world,” Slotkin writes..."

"Why on earth would Lincoln suffer such insubordination?"

"McClellan had finally gone to battle, and won, but the victory proved to be his undoing, not the coronation he’d imagined in his letters to his wife."
Better idea: if you're going to write history, write about historical persons, not literary characters.

Also, never, ever refer to "McClellan's letters to his wife" if you want to be taken seriously as something other than a novelist.