Looking for something to read? Library Thing will let you go the usual Amazon route where things are recommended based on what you like. But, more interestingly, it will also let you type in a book you love and tell you what books you will hate based on that.
If one of your favorites is Immanuel Kant’s Critique of Pure Reason, it tells you that you will loathe Confessions of a Shopaholic. This is based on information about people’s actual bookshelves, so in the examples I typed in it was entirely accurate. Not to self: Never read Real Men Don’t Apologize by Jim Belushi, the internet tells me I would hate it. Well, that and common sense.