Welcome to nonfiction writing! It must be quite a transition from filmmaking to compiling biographies.
You have done very well for yourself, landing a major book contract with a big trade house (FSG), your subject being an obscure Civil War officer who briefly served as McClellan's ADC.
There is no Irvin McDowell biography yet, but we at least have one of Charles Russell Lowell, Jr., thanks to yourself and your publisher. And why not?!
Now, if I could give a few little tips.
As your subject is connected to George B. McClellan, it would be good to know something about General McClellan. For instance, you might want to correct the next edition of your work so that it does not say that Lowell's fellow aide Arthur McClellan was the general's nephew. Arthur was his brother.
You also have to be alert for footnote readers, a sly bunch, quick to argue, quick to find fault. When you make a statement like this, it sends the footnote readers scurrying: "As part of his [McClellan's] efforts to improve morale and to gain publicity, he frequently staged grand reviews, and the army was often paraded through Washington."
The footnote reader is intrigued by the possibility that you have a source for McClellan trying to gain publicity - that would be a fine catch for a researcher. This kind of reader is also challenged by the comment "frequently" set next to grand reviews as well as the assertion "often paraded through Washington."
Your humble and ignorant correspondent is wracking his brain for the exact number of grand reviews and is coming up with two, only one of which was staged in Washington. In despair of his own ignorance, he turns to your endnote for clarification, where he sees, "For more information on General McClellan, see Stephen W. Sears..."
Was that an "appeal to authority" in lieu of data? Hmmm. You know the learned genlemen who accepted your nomination for this year's Lincoln Prize may not approve of that kind of thing.
They may also be surprised, if they ever read your book, to see that Salmon Chase was a senator from Pennsylvania.
I know Goodwin beat you for the prize this year, I hope that Chase thing didn't do it.
I hope, also, that it wasn't your loose, pop-history language that gave the game to Doris. When you say that David Hunter was "an early convert to the use of black troops" it makes it sound as if Hunter bought in to someone else's earlier idea for USCT regiments. I think Hunter could reasonably be called the source of the idea, Carol.
And Carol, note this: Hunter armed slaves - he was not smoking a cigar in his study when he came up with a futuristic concept for USCT regiments. No, Hunter armed runaway slaves for combat operations against the CSA as federal volunteers in the early war. Does that seem like an interesting point to you? You see how that might add a little more juice to your story than He was an early conver to the idea that... ?
No? Oh well, then there's no use trotting out all these other points I've made out.
Carol, you've lost the Lincoln Prize but you are utterly and totally Pulitzer worthy, the Pulitzers being what they are nowadays.
Your pained but faithful reader,