Yesterday I listened to Open Book on Radio 4 (available on
iPlayer, at least in the UK). There's a section about e-books and best seller lists (from around 09:30 to 16:30).
Apparently e-books aren't included in best seller lists, at least in the UK, because Amazon have the lion's share of the e-book market, and won't tell anyone how many Kindle books they sell. The program seems to suggest that if Amazon don't release sales figures, then there's no way around that. Presumably, though, the publishers know how many books they have sold, so why can't traditionally published e-books be included in the lists?