“Free: the past and future of a radical price” – a book by Chris Anderson

This book is about the 21st century meaning of “free”, which really means you don’t have to pay anything… as opposed to the 20th century meaning of free, which meant that there’s a hidden cost somewhere.

The book is available as a book (for instance on www.amazon.de, www.amazon.com), with a small cost, or as an audiobook for FREE (the abridged version actually costs something… well time is money!)
http://www.hyperionbooks.com/free/free_downloads.htm
http://www.wired.com/images/multimedia/free/FREE_Audiobook_unabridged.zip