Readgeek is an online book recommendations engine and social cataloging service launched in December 2010.

The website allows users to search for books matching their individual taste making use of several algorithms.

Taking ratings and metadata of prior read books into account, those algorithms help the site to learn about a users preferences.

The service suggests books other users with similar tastes have enjoyed, rather than offering up books similar to the ones a user already ranked.

[1] It is the first of its kind to give users a prediction of how much they will like almost any book.