Seconding _Blindsight_, which is a great book (which he describes as 'a philosophical rumination on the nature of consciousness with an unhealthy focus on space vampires') You won't think about consciousness the same way again. And it's free!
This book also led me to discover _Portia Labiata_, a bewilderingly intelligent spider --- and so cute! https://www.flickr.com/photos/hirzi/6285232356 There's an accessible paper on what makes it so interesting here: http://www.researchgate.net/profile/Duane_Harland/publicatio... I wonder if Watts' suggestion that it timeshares its brain has any truth to it?
_Echopraxia_ is also superb, but I thought it was disappointingly similar to _Blindsight_. That doesn't mean it's not in any way a good book, but it's very much based on the same themes.
Be aware that the book called _Firefall_ is an omnibus edition of both books.
I haven't read any of the Rifters books. Worth checking out?