The jury is still out on why this happened. Amazon says that there might have been some odd glitch, while a "famous" hacker, Weev, is claiming he pulled off the prank.
Whatever. Its annoying but is being rectified apparently, so isn't worth getting too many panties bunched up about...
But! For a while, despite removing most of the gay literature, there were plenty of anti-gay books that remained in the normal category. As a result, this book popped up as the first hit when searching "homosexuality" on Amazon:
Check it out for yourself.
But when you are done looking on in aghast horror, take a peek at the "User Submitted Pictures" associated with the book.
O... M... G...
(pst... Its in the upper left hand corner, just under the book picture.)