I first read this book about 20 years ago - pretty much in one sitting on a wet weekend in Felixstowe. Found it again in the loft and pretty much repeated the one sitting reading. Excellent, hard core science fiction. Incredibly thought provoking - you're sitting there thinking - "impossible, how could life possibly evolve in such conditions, how could particles arrange themselves into such complex patterns, etc, reproduce and ultimately become sentient. Poppycock. Unlike here on Earth, where we totally understand how simple the emergence of Life was here, etc....." Big ideas and concepts as well as some interesting physics. Ok, Forward's human characters may not be that complex - but then I've never reckoned that Arthur C. Clarke could create a good character - besides, the book isn't really about the humans. A great read, and "Starquake" is essential reading if you find this book in any way interesting.