The Book Seer is a web application for recommending books. It takes the last book you read, and searches a number of other sites – Amazon, LibraryThing and BookArmy – to offer a suggested list of books to read next. It does this using those services’ publicly-available APIs.
Bookseer proved immediately popular, being picked up across the web, notably on the Guardian Books blog.
The Book Seer offers people a short list of books from a range of sources in an informal way.