They are getting data directly from Amazon regarding sales of e-books- shocking, since Amazon has been so tight lipped about Kindle& eBooks sales in general. A quick look today showed no E-books in the list of the top 150 books… hmm. So, how are things really going Amazon? :P
I'm not the only one suspicious of Amazon (an e-book proponents in general) playing a bit of a shell game here. See Motoko Rich's blog post 'Lost Symbol' Also a Big Hit on Kindle, But How Big? In particular, this bit is very telling "But it seems that the breathless reception of Amazon's news is a little overblown. Although Knopf Doubleday, which printed 5 million hardcover copies of "The Lost Symbol," has declined to say what proportion of the more 1 one million copies of hardcover and e-book editions it sold on the first day of the book's release were actually in digital form, a person familiar with the sales figures said far less than 5 percent were electronic book editions."