Scott Sigler was a writer that decided to write a book, do a reading of it episodically as a podcast and hope that it would generate enough publicity for him to get a bookdeal out of it.
Well Earthcore was a huge success and you can buy the book from Amazon.com or subscribe to the podcast and download all the episodes for the website.
I didn't listen to Earthcore because I slept through the first two episodes so I didn't get into it, but I have started listening to his new book Ancester (currently on episode three) and after a slow start (just episode one), has started to get very interesting. If you like audiobooks, especially free audiobooks I suggest you signup to the Feed (iTunes).
I should mention that iTune's feeds are a bad way to go for all podcasts because Apple doesn't update the database very often and you can be left waiting weeks for them to update. So I suggest you use the XML directly from the site instead. Unless it is something like Podfinder or iTunes New Music Thursday (sorry no link because it seems to have disappeared from the database for now) in which case don't have webfeeds.