Blightsight by Peter Watts previously, it's one of my favourite books, as well as being one of the cleverest in terms of delivering fascinating and advanced concepts in an accurate and accessable way. It's a rare book which can do this, retaining the science, without losing the story, or vice versa.
The book concerns humanity's first attempt to contact an alien species, a fairly classic science fiction trope, and one richly deserving of having new life pumped into it. The narrator is a member of the crew, who is tasked with the job of watching the remaining crew, so he can report back to Earth as to what is occuring on the ship. The reason for this addition, the crew is comprised of individuals who have been radically altered from the human baseline, and thus are incomprehensible to 'normal' human beings at times.
The book's science ranges widely throughout, from biology, to physics, to neurology. The author comes up with one of the most consistent and logical explanations for vampires that has ever been done, and the alien's the crew encounter are one of the rare examples of a truly alien existance. However, the core of the book concerns are about conciousness and what it means to be intelligent. Also explored is the idea of different types of conciousness, and whether damaged (in terms of mental illness) minds can be as valuable as what we currently call 'normal'.
I don't want to spoil the plot for anyone who goes on to read this, as it's too well constructed to want to interfere with the voyage the author takes the reader on. Suffice it to say, by the end, the reader is left wondering if the "I" behind their eyes is as valuable as they have thought all their lives.
The other rather wonderful feature of this book is that it can be obtained for free from Peter Watt's website (which I have linked at the top). PDF and ebook variants are all avaliable. Go forth and obtain a copy, and if you like it, I'm sure Watts will be happy to take your money.