An intriguing Big Idea, as you would expect, and a brisk narrative pace despite the fact that little happens. I was left with the taste of the book's flaws more than its virtues: Part one (of three) is mostly academic politics, meetings and beard-stroking; part two is mostly aliens talking to themselves. Part three has more narrative flow than the other two, but is irredeemable. One character's importance to the plot is pulled out of (a hat), another's nefarious motivation seems tacked on to the end... too many flaws to enjoy properly. Not, as you may gather, Asimov's best.