"The author's considerable explanatory material and supportive evidence could have been reduced with proper editing. A multipage discussion of how mortar boats could have been employed against Yorktown is one example. Historian James McPherson's advice "not to tell the reader more than he wants to know" is applicable."
Ughh. Can't we please put this particular McPhersonian commandment to bed? If this strange statement were ever applicable to CW non-fiction, I should think Beatie would be the least of candidates for it. He is constructing a broad study of the Union's war in the east from the ground up using a vast array of primary sources, much of it new; "considerable explanatory material and supportive evidence" is kinda useful to the project...more like obligatory.
To get back to generalities, it's not the first time I've seen reviewers resort to this pronouncement. Taken out of context, I seriously doubt McPherson meant for it to apply to all forms of Civil War non-fiction literature anyway. Unfortunately, many reviewers don't see the distinction. When used in the manner of a general truth, the statement promotes a completely wrongheaded notion of the CW author-reader relationship. Infantilizing the prospective audience of readers doesn't strike me as a useful advancement; and just how does an author or publisher determine 'what the reader wants to know' anyway? Who is "the" reader? I daresay I would prefer a book written by a meticulous and driven Civil War author whose prospective audience is only himself rather than one directed toward a falsely imagined general reader.
As for the other point made of "proper editing". I wish it would occur to more critics that lengthy asides involving reams of background material and weight of evidence can be essential parts of the journey--or even perhaps the point of it all. Some reviewers seem at a loss when confronted with works that break the 'rules' of narrative history. If a sidebar takes you off track, so what? Who hasn't followed directions somewhere only to find that travelling down a 'wrong' turn or a trail off the beaten path has placed you at an even more interesting destination.