We looked at the state of Civil War book sales last year, not taking a "pure" industry view but specifically estimating the commercial strength of authors championing Centennial doctrines (McPherson, Sears, Gallagher, Catton, Nevins, Davis, etc.). This link points to a post summarizing conclusions with links to each individual article in the series.
You might want to review that material as we ease into a mid-year analysis of Civil War sales trends in 2005. That series will start later today or tomorrow and run for at least five posts.
To understand basic publishing lingo and the rule of thumb for estimating the sales of individual authors, be sure to read this in particular, and this too.