This one is much like the prior novel (which you should definitely read first), only now travel between universes is easy, and the language issue is essentially solved.
The rape scene in the first book is now the basis for other things, though it's still kind of smarmy-feeling.
More inter-societal philosophy exchange; and politics which runs entirely too smoothly.
It's a reasonably enjoyable book. It gets up to four stars. But the "new ideas" of the prior novel really aren't here.
4 of 5 stars.
Some of the events are fantastic and improbable, but Sawyer handles the pace well. A great ending and a satisfying read.
Robert Sawyer appears to take great pains, if not pleasure, making the reader think about our basic assumptions of ourselves and our civilization(s). He does this by deliberating posing questions from an offworld visitor - in this case another kind of human (home neanderthalis) instead of off-world alien. Whether or not you believe the sci-fi part is possible (don't want to open up another can of worms in quantum vs. string physics!), can a rational and scientifically based culture co-exist with our more emotional and political nations? The discussion at the Vietnam Memorial illustrates this dicotomy for our homo sapien stand-in, Mary. He even brings in that scientific argument about the nature of the universe: do we really need either a Big Bang or a creator, or has the universe always been present?
Lotsa questions that some may not enjoy thinking about. So if you like ray guns and rampaging or benevolent aliens, this is not the series for you. But if you don't mind re-examining yourself, then jump in and join the debate.