Mystery authors dominating Amazon bestsellers list

Out of curiosity, I checked what Amazon's 100 biggest selling fantasy and SF novels are right now. It's updated hourly, so the link above will give different information over time, but you can still draw some interesting information from it as a snapshot.

• All but one of the top ten are either by J K Rowling or George R R Martin, and I can't see that changing much for a while.
• Rowling and Martin together provide 14 of the top 100 entries.
• The only other authors to have 2 books in the top 100 are Terry Pratchett and Stephen Baxter, jointly for their Long Earth series.
• Nearly 1 in 5 (19) are there as £1 or less deals.
• Over 1 in 4 (27) are there are £2 or less deals.
• Most of the cheap books are for authors I've never heard of, Peter Hamilton excepted. That doesn't make them bad, of course, just unknown to me.
• Authors known to me other than Rowling and Martin make up only 15 of the top 100.  And I'm reasonably widely read and have good name recognition for authors I see on the shelves.
• No, the unknown authors aren't just urban fantasy romances (although some are).
• No, they aren't other genres mistagged (with one or two honourable exceptions).
• Add in Rowling and Martin to the other known authors, compensate for imperfect knowledge and I'm still wondering who 3 in 5 of these best selling authors are.

Intriguing: is this the self-publishing revolution in action? Further analysis required.