Very dense, hard sci-fi. Not going to lie, I was only *just* keeping my head above water at times. The discussions in this book were fascinating, but it wasn't entirely successful as a story. The narrator reflecting on his past too often took me out of the flow, unfortunately relieving the tension (which was otherwise juicy). At times there were so many ideas packed into a section that it felt bloated, which was unfortunate - your preference for story/idea balance will affect your mileage with this book. I think it will make for a rewarding re-read one day, though, so that's a good sign.