Blindsight is a neurological condition where there's nothing wrong with your eyes, but you cannot see. Your brain cannot access the image data consciously, but you are still able to reflexively react to visual stimuli, such as by ducking an object flying at you. Blindsight is kind of related to the perhaps more famous condition of body integrity identity disorder, where one might think that their leg or some other limb is not theirs but just a dead piece of meat and needs to be amputated.
Blindsight, on the other hand, is a 2006 novel by Peter Watts. The events of the story take place in the 2080s, when a spaceship called Theseus is sent to investigate an alien object somewhere far beyond the Kuiper belt. Technology has advanced greatly since our days. 3D printers, called fabricators, can print just about anything, including computers and robots. Medical treatment can also cure almost anything short of a major brain damage, including severe radiation poisonings. People get their brain rewired for attitude adjustments and DNA augmentation isn't uncommon either. The minds of deceased people are copied into a virtual world called Heaven, and the living can visit them there.
The story follows the events in and around Theseus. The crew consists of an AI called the Captain and five people: Siri Keeton, Susan James, major Amanda Bates, Isaac Szpindel and Jukka Sarasti. Keeton is a synthesist, trained (with the help of some brain augmentations) to understand complex systems and to explain them to others. He is also the narrator of the story and is included in the crew to observe everything that happens and report back to Earth regularly. Susan James is the "mother" of the Gang of Four, the other minds living in her brain: regularly any of the Gang of Four may take control of their common body, and together they form a highly functional unit specialized in linguistics, to speak with the aliens. Amanda Bates is the soldier in case things get bad, and Isaac Szpindel is the biologist, to study the aliens. Finally, Jukka Sarasti is the commander in charge of the operation. He is also a vampire, brought back from extinction by the science of paleogenetics.
If at this point you flinched, don't. Vampires aren't some magical creatures, but the author has actually devised a plausible evolutionary history for Homo sapiens vampiris. It is, for example, noted that vampires are sociopaths: "Vampires had to be sociopaths. They're too much like their own prey—a lot of taxonomists don't even consider them a subspecies, you know that? [...] If the only thing you can eat is your own kind, empathy is gonna be the first thing that goes. Psychopathy's no disorder in those shoes, eh? Just a survival strategy." The reason why there's a vampire commanding the crew is that vampires have superior pattern-matching and analytic skills compared to humans. It's basically hinted that in a traditional IQ test a vampire could score four digit numbers, whereas the average human IQ is 100. That makes sense, since if you are going to hunt something as clever as man, you'd better be smarter than your prey. Additionally, vampires are solitary hunters: very territorial and never team up.
In many works of fiction long distances in space are covered in some kind of cryogenic sleep. Watts has cleverly combined this with vampires, as the crew's DNA has been augmented with some vampire DNA, allowing them to be "dead" for a long period of time and then be woken up again.
Regarding Susan James, it's important to note that the Gang of Four (her and Michelle, Sascha and Cruncher, who is the only male in the gang) aren't Susan's alter egos or anything like that, but indeed completely other people. While Susan's brain has become "multi-core" with the help of a surgery, it is noted that a simple, strong enough stress could also split the brain the same way. The story makes a clever remark about the multi-core people of the past: "People were fucking barbarians about multicores back then—called it a disorder, treated it like some kind of disease. And their idea of a cure was to keep one of the cores and murder all the others. Not that they called it murder, of course.".
A few times during the book there's a nice recurring narrational feature, where a section would start with "Imagine you are [someone or something]" and the story would progress for a while describing what you usually do and how you usually think, and reflect that to the events at hand. That's a nice break from the other narration and I haven't seen it used in other books. Just when you might think the trick is getting old, it disappears for a couple of hundred pages, just to resurface to wrap the entire story up. So the narration (as well as the vocabulary) is clearly way, way above that of, say, Dan Brown's works.
On the cover of the book there's a quote from a British author Charles Stross: "Blindsight is a tour de force, redefining the First Contact story for good.". That should already give it away that aliens are indeed encountered when Theseus reaches its target. But what do you do when you don't even know if the aliens are way smarter than you, or if they are as stupid as dandelions? The book explores interesting concepts such as the Chinese room and the relationship between sentience and intelligence. The author has clearly seen a lot of trouble making everything so different from other stories, yet plausible, and also manages to make you think.
I recommend the book for anyone interested in hard-SF. I'd also recommend the novel for anyone who's not interested in science fiction, as this might be a good starting point with the more realistic setup than, say, Star Trek. The author has published the entire book on his web site at Rifters.com in PDF and HTML formats as well as in some e-book formats.