Some very interesting stuff here:
Particularly scary was the revelation that 200,000 books are published each year and your average branch of Waterstones can only stock 30,000 books (and that includes the classics) so, if if your book is listed on Amazon that doesn't guarantee it's actually in bookshops.
And what of the supermarkets? How do they decide what to stock? The discussion on the importance of a novel's cover is an interesting one...