I can not agree more with the authors that Book Industry has lagged behind music and movie in terms of being able to help users find books that they might want to read based on various factors. The reason for this is that Book Industry has not yet gone beyond collecting basic metadata elements about the books (price, no of pages, author, publisher, year of publication and genre) and used these basic metadata elements to filter down books. But I believe for an effective targeting system to work we would have to collect more granular/soft data about these books like mood of the book, Kind of ending, Male vs Female characters, Era etc that define the content better and thus could be used to effectively match the book to the users mood and taste.
I am sure someone soon would come up with a model to do so. Looking forward to that start-up. Great idea for us also 🙂