[NightBird]

Here's another one:

Booklamp is a slightly more sophisticated version of Whichbook with a very in-depth study for each book, making new book “matches” for users very effective.

Upon completing the simple sign up process, users are given the option to view their book matches, use the forums, or suggest books to be reviewed. Upon selecting the option to view your book matches, it offers a very thorough book search by plot – booklamp will give you a list of approximately 500+ books currently in the database and a descriptive look at each, including the number of words, number of scenes, as well as the scale and intensity of the dialog, description, action, density, and pacing for each scene throughout the entire book, then pair it with other books based on the same characteristics and give you a scale as to how closely other books relate (e.g. 98.7%)

http://beta.booklamp.org/