One fundamental point that tends to get overlooked is that unlike CDs or cassette tapes before them, books traditionally came with built-in DRM, insofar as copying them (via scan/OCR/proofread) was a really tedious process. Whereas it's relatively easy to crack the DRM on, for example, MobiPocket or Microsoft Reader books (and probably ePub by now). So the DRM'd formats are easier to pirate than the previous "analog"-analog format. What this portends for the future remains to be seen, but wearing my full-time novelist hat, I'm a bit worried. The music industry has efficiently trained people to grab files without throwing money at the artists, by bringing the role of publishers into disrepute. Now we're all set to repeat the experience, and unlike a rock band, most authors don't perform well on stage.

Note that any sales figure a major English language publishing house discloses will be inflated by between 50% and 300%. This is standard practice -- everybody does it, so if you don't do it, everybody will assume that you're exaggerating your sales anyway and discount the figure accordingly. Stupid, but that's the way the business works. Even if you assume the 6.5 million worldwide sales figures is exaggerated by a factor of three, that's hugely impressive -- an SF novel that sells 10,000 hardcover and 50,000 paperback in the US is doing really well (and you can triple that figure to get an estimate of the worldwide sales).

Terry Pratchett's total career sales track is around 66 million books. Steven King sold somewhere upwards of 100 million, total. J. K. Rowling is around the 70-120 million mark, worldwide. I call bullshit, by at least one (and probably two) orders of magnitude.