A few days back I had linked to a site that recommended further readings based on your favorites or what you are reading currently.
Here's a site that does the opposite. Enter a book that you dislike, and the UnSuggester will tell you which other books to avoid.
The UnSuggester reminded me of the Worst Books Ever/The Most Overrated Books meme (an offshoot of an earlier book tag meme) that did the rounds of the Indian blogosphere roughly a year and a half back. These are the results from the Unsuggester for some of the books I had mentioned in that meme:
One by Richard Bach
Who Moved my Cheese? by Spencer Johnson
The Alchemist by Paulo Cohelo