I suspect the average SF fiction reader will be more tech savvy than the average ancient history reader
Again, why? The topic doesn't determine the tech-savvyness of its readers, at least not in the way you suggest. Particularly, ancient history is an academic subject, and it will likely follow the general pattern in academia, with younger people being more acquainted with technology (with minority exceptions in both directions).
Consider dinosaurs: I don't think there is a less tech-heavy topic (unless the poor dinos used computers, dunno), but I'm pretty sure that a vast majority of people interested in them have been familiar with computers at least since college age.
Ok, well, I guess you could be right, I don't know -- it wasn't really the point of why I mentioned it.
As you can see, I used the example SF versus history to illustrate that the sales statistics of ebooks versus print can be different depending upon the author's target audience, which I think is true: I don't believe the percentage sales of ebooks versus print is the same in all categories. When used as an argument why the printed book is dying, we should therefore put the sales numbers from one author in this perspective.
Again, why? The topic doesn't determine the tech-savvyness of its readers, at least not in the way you suggest. Particularly, ancient history is an academic subject, and it will likely follow the general pattern in academia, with younger people being more acquainted with technology (with minority exceptions in both directions).
Consider dinosaurs: I don't think there is a less tech-heavy topic (unless the poor dinos used computers, dunno), but I'm pretty sure that a vast majority of people interested in them have been familiar with computers at least since college age.