Discount bookshops are a hunting ground of both pleasure and pain for me, a soon-to-be-published author, and independent bookshop employee. To see all those unsold/returned/unsellable books stacked up, it tends to break your heart a bit. Still, there are reasons books end up in the discount pile. My most recent trip to Brisbane's biggest discount book graveyard reminded me of a few of them...
#1 One spin-off too many
#2 Books with coloured pages
#3 Books that don't fit on any regular bookshelf
#Books that have to be pulped once their subjects turn out to be a deeply dodgy probable rapist. Or Matthew Johns.