I occasionally check the Amazon rankings to see how the book is doing. I don't know how many copies have actually been sold, but I can see where it ranks in relation to other books. Yesterday was a good day - For the first time (as far as I know), "Forts" was ranked in the top ten of new titles from Stackpole Books!
I'm very happy about this. Stackpole released 72 new titles for the fall season, most of which cover their stock in trade. They have the very popular "Stackpole Military History Series" which covers World War II in depth and has almost two dozen new books in that, plus a good number of new books on fly fishing, crafts and mid-Atlantic tourism (Stackpole is in Pennsylvania). "Forts" isn't a featured new title on their home page and as the Midwest population is quite a bit lower than the mid-Atlantic, I can't complain!