An interesting note: over the past 4-6 weeks, my Bookscan numbers have been moving steadily up. They hit a low of about 29 copies and this week hit 79. Almost all of the increase is due to increasing sales of GCA. The interesting thing is that this isn't an up-down jumpy thing, it's been a fairly smooth progression: 29, 30, 41, 49, 72, 79. It may be leveling out and ready to drop again, of course, but the interesting part is that this is the kind of spike you expect to see when some fairly broad SOMETHING gets people's attention, or when a book first hits a market. There doesn't SEEM to be a specific geographic distribution for it, though.
The only thing I can think of is the liquidation of Borders. Have other authors seen the same thing?