I just finished Peter Watts Blindsight. Wonderful read and quite thought provoking. It plays with the idea of intelligence without sentience. Interesting. All of Watts' books are available for free at
www.rifters.com
I consider his other books, Starfish, Maelstrom and Behemoth, to be must-reads, also. I've read all his stuff as ebooks, but am going to buy them all in hard copy to add to my permanent library.