Wow! This is going to be a different kind of review for me. I can honestly say I'm not sure I understand what happened in this book, but I kept reading because I felt some underlying "thing" driving me to the end.
First, the problems:
I never felt grounded in Watts' world. Terms to describe the society were never explained. I guess he thought I was smarter than I am? This was almost as annoying as when authors explain everything as if I were stupid. Here is another example where there is a fine line marking how we gauge the intelligence of our readers. (I do read hard sci fi and enjoy it. The trick is giving me just enough info to follow the science--I don't feel like I got it here).
I could never picture any of the characters. Not physically anyway.
The main character and narrator had half of his brain removed as a child and it happened to be the side that processed emotions. Thus I never connected emotionally with the MC. Or anyone else for that matter.
So why did I keep reading to the end?
The plot was compelling enough that I just had to know what the heck was going on and I hoped there would eventually be some kind of explanation I could understand. Here, let's try this.
What I think might have happened in the book (possible spoilers, but I'm not sure):
Siri (MC) had seizures as a child, so his parents had half of his brain cut out and replaced with inlays to fix it. Society (this is on earth) had developed to a point where most people were full of wiring and electrical gadgets built in that the was normal.
To be useful, you specialized in specific inlays or upgrades. If you didn't want to be useful you just plugged your brain into Heaven to create your own realities while your body rotted in a vault. (I wish more of THIS had been discussed.)
Anyway, Siri was the synthesizer--meaning he gathered info through observation of "topography" or body language, compiled it and sent it back to whoever hired him. He doesn't even have to speak the language of those involved he is so good at this.
So, there is a threat and he's sent out into space with a small crew to do something. None of them really know what. They wake up from cryosleep and spend most of the book observing this thing. The ongoing question boils down to sentience versus intelligence. What is the norm of the universe?
People and aliens die. The vampire broods, spazzes out, is possessed by the ship (if he was ever his own person to begin with is debatable). Everyone is played. Heaven is unplugged by radicals. In the end, Siri goes crazy or becomes human again. The end.
Oh, and the title? Blindsight has something to do with your brain stem. Its the part of you that sees what the rest of your brain doesn't believe is possible. That shadowy movement you catch in the corner of your vision that disappears when you focus on it kind of thing.