My client and friend Luis Gonzalez, co-head of the GSR Foundation, sends me an article highlighting the incredible growth of Goodreads social reading site, with 20 million unique visitors per month.

It is remarkable that in these social media times authors can sell over 13,000 books to their fans. And a lot -as many as 35,000- of self-promoting, social-networking authors have taken to Goodreads.

The site currently has 20,000 groups and 8 million registered members who have written more than 13 million reviews and bought more than 280 million e-books.

One of the great tech features of Goodreads is its next-book-you-should-read recommendation engine. This algorithm is based around ratings, what's on reader's virtual bookshelf and what readers with similar tastes have recommended.

Also, for self-promoting authors, bloggers and publishers is a fantastic tool.