I heard about the UnSuggester in the latest Chronicle of Higher Education.
Unsuggester takes “people who like this also like that” and turns it on its head. It analyzes the thirteen million books LibraryThing members have recorded as owned or read, and comes back with books least likely to share a library with the book you suggest. The unsuggestions come from LibraryThing data, not from Amazon. LibraryThing also produces great suggestions.
For instance, if you are a fan of Seven Storey Mountain, it suggests you probably won’t like Stephen King’s Dark Tower. If you like The Confessions of St. Augustine, you probably won’t be reading Night Pleasures by Sherrilyn Kenyon. If Left Behind is your thing, various works by Eveylyn Waugh are probably not on your shelf. If you heed The Screwtape Letters, you are probably not tempted by various tempting titles.
On the other hand, the BookSuggester seeks to give you helpful advice on things you might want to consider.
For example, if you like Seven Storey Mountain, consider other works by Merton, or Kathleen Norris’ Cloister Walk, or Chesterton’s Orthodoxy, or Bonhoeffer’s Cost of Discipleship. If Augustine’s Confessions causes you to reflect on your spiritual journey, then Bunyan’s Pilgrim’s Progress might lead you further down that path. If you are in fear of being Left Behind, you might enjoy being scared by books by Frank Peretti or might want to make the most of the present life by reading The Purpose-Driven Life. If you like Screwtape, consider Sheldon Vanaukan, A Severe Mercy, or Thomas a Kempis, The Imitation of Christ.