Wikipedia
Shelfari is a social cataloging website for books. Shelfari users build virtual bookshelves of the titles they own or have read, and can rate, review, tag, and discuss their books. Users can also create groups that other members may join, create discussions, and talk about books, or other topics. Recommendations can be sent to friends on the site for what books to read.
Shelfari was launched on October 11, 2006. In February 2007, Amazon.com invested $1 million in Shelfari, and moved to acquire it a year later in August 2008.
As of January 2016, the site hosts a notification announcing "Shelfari is merging with Goodreads".
As of June 2016, the site is decommissioned (all links redirect to Goodreads). Despite mention of a merger, users complain that the most important Shelfari features have not been merged (primarily that the comments system doesn't allow detailed discussions of books, and background information on each book's main characters has been discarded).