Great book - unique story and a very different read for me. I've read some sci-fi before, but very little as "hard" sci-fi as this. There were a few places where the "technicalities" made me almost skim the text a bit, but I persevered and I was rewarded :)
The story and the characters are really well-written and fascinating, and I personally like how I had no real problem imagining that most of the storyline could happen (you know, if we had spaceships and that).
Over the years, I've become more and more fond of the storytelling "method" of don't show, don't tell, but keep me guessing and imagining :) I personally liked that so many things were mysterious and sort of left to our own imaginings, but I can see how it can maybe not be for anyone who expects an "explained" story with a concrete conclusion.
I think it's one of the book's greatest strengths. In the end, had I been more of an actual sci-fi fan, this would likely had been close to a five (or at least 4.5)
Absolutely recommended - I will be looking forward to reading Clarke's Space Odyssey.