Rating: 
Summary: Excellent portrayal of strong AI and its implications
Review: Greg Egan is the first fiction writer I've seen who takes the concept of AI somewhat seriously (see my detractions below). In virtually all science fiction, AI is either not present (Dune), artificially rare (Star Wars, William Gibson), somehow deficient relative to the "real" intelligence of humans (Star Trek), or easily tamed into servitude (Asimov). Egan thankfully avoids these lame cop-outs and provides a more realistic view of what might happen when our hardware can support human-mind-scale computation.Some of the extrapolation is fairly straightforward, for example the idea that the first humans to have themselves "scanned" and instantiated within a computer as Copies will be the elderly and the fatally ill. Egan goes many orders beyond the straightforward, however, and hits on some big questions: If I get moved into a computer, is it still "me"? Should sentient software be considered legally human? If I am a program running in a computer and I edit my memories and my most basic desires, have I become a new person? If I halt a Copy's program and archive their data indefinitely, have I "killed" the Copy? What would it be like to be forced to live forever within a computer, with no ability to commit suicide ("bail out")? If these are interesting philosophical questions today, they will become much more tangible over the coming decades as (or if, depending on your view) AI develops. Now, my caveats/complaints. A book that seriously considers AI must, I think, include the possibility of super-human AI as well. And Egan, like almost all other authors, conveniently leaves this possibility out. For example, in Permutation City there is an unexplained 17x slowdown of Copies relative to real time. In truth if the average Copy runs at a 17x slowdown, the millionaires among us would cobble together enough supercomputing power to run at a rate equivalent to real time. And the billionaires would have enough hardware to run laps around flesh-and-blood humans. I could easily envision a scenario where every company that doesn't have a management team of hyperspeed Copies would be left in the dust. But Egan tends to stay away from these kinds of unpleasant they-will-become-our-masters scenarios. (In another book of his called Diaspora, Egan does allow for faster-than-human robots called gleisners, but again assumes they will treat is well -- basically a variant of Asimov's stunted-AI). I would love to see Egan put on the Bill Joy hat and deal with superhuman intelligences fairly. The second half of the book relies very heavily on the author's intriguing "Dust Theory". While I don't necessarily find the idea very compelling as a physical theory, it does touch on some ideas that could very well have validity, such as the notion that a universe will exist if it has internal mathematical consistency (the Platonic view to its logical conclusion). Unfortunately at some points in the story the Dust Theory feels like a cheap trick, a bit of magic that can push the story in whatever arbitrary direction the author desires. In this respect the plot is like a French art film: locally rational, globally irrational. Despite the detractions, I enjoyed the book immensely and found the ending surprisingly poignant. Read it especially if you are intrigued by the notion of strong AI.
Rating: 
Summary: Permutation City
Review: Greg Egan must have an incredible amount of intelligence when it comes to technology. Either that, or he has a masterful imagination. A combination of both, I am sure, were used in the writing of Permutation City. Egan uses technological advances in his novel that are above and beyond what is possible in today¡¯s society. Egan was also able to define the society, and be very precise in doing so. Egan was also able to develop a well-written story line that mixes in with all of the technology. By doing so, this book can keep you reading, even if you are not really into a lot of science fiction. Permutation City is a good novel to read if you are a hardcore fan of cyberpunk novels. This book is an example of science fiction at its best. If you are not a fan of science fiction, this book is probably not for you. The main character Paul Durham is a human that has been copied onto a code, and loaded onto a computer. Paul was then just a copy of a file, and no longer a physical human. Paul still has his human body on the outside, in the ¡°real world,¡± but his physical self has blocked Paul¡¯s option to ¡°bail out¡± of the computer and regain his real self again. The rest of the novel goes through Paul¡¯s (the copy) thoughts and actions, as he attempts to regain his physical body, and the entrance back to the real world. I thought that overall, the book was pretty good, and worth my time to read. I only have a few criticisms of the novel. The ending is not quite what I would have liked; as with many other cyberpunk novels, the author spends a lot of time giving you a story line, only to give you a sub-par ending. Another criticism I have of the book has to do with all of the technology. I found that a few of the things (the ¡°Autoverse,¡± as an example) to be a little bit too confusing. Once I was able to straighten it all out (by rereading certain sections multiple times), I was able to enjoy the novel a lot more. All in all, I would say that I did like the novel, and I would recommend Permutation City as a definite book worth reading!
Rating: 
Summary: Thought provoking certainly but not enjoyable!
Review: I agree with much of prior reviewers comments about this book. Definitely thought provoking (but that could be done, and was done in a few pages). I found it meandered, lost its way, was generally hard work reading, and ultlimately I finished it because I had started it rather than I was getting any enjoyment out of it. SF is definitely my preferred reading matter, but htis is the first I have read of Greg Egan. Don't know if I will try any more Egan.
Rating:
Summary: Interesting concept, but a little thick
Review: I bought Permutation City after seeing it referenced in an article on the existence of alternate universes in Scientific American. Having a casual interest in the subject, I thought I might enjoy the book. And I did, but I would not recommend it to casual sci-fi fans. I count myself among that group, and thought the story bogged down far too often in psudo-scientific detail. Hard core fans of the genre may be more accepting of this, and the premise itself is a compelling one. This is what kept me reading, despite the psudo-science that was in truth over my head and characters that were flat and somewhat underdeveloped. If you're not interested in AI or alternate universes, I suggest you steer clear of this one, but if they strike your fancy, its worth reading for the novelty if nothing else.
Rating:
Summary: Interesting concept, but a little thick
Review: I bought Permutation City after seeing it referenced in an article on the existence of alternate universes in Scientific American. Having a casual interest in the subject, I thought I might enjoy the book. And I did, but I would not recommend it to casual sci-fi fans. I count myself among that group, and thought the story bogged down far too often in psudo-scientific detail. Hard core fans of the genre may be more accepting of this, and the premise itself is a compelling one. This is what kept me reading, despite the psudo-science that was in truth over my head and characters that were flat and somewhat underdeveloped. If you're not interested in AI or alternate universes, I suggest you steer clear of this one, but if they strike your fancy, its worth reading for the novelty if nothing else.
Rating:
Summary: I AM STILL MIDWAY...
Review: I haven't really finished the book & I find it very tempting to simply give up, close the pages & stuff the book in my shelf. Although I enjoy reading 'sci-fi" books, I find this too technical & unfortunately, I really do not appreciate it as much. However, after seeing the other readers' comments, I feel inspired to continue reading the book till the end no matter how much effort it might take me to do so. Hopefully, I will have a better opinion to share with afterwards.
Rating:
Summary: Long term impact.
Review: I still sit and ponder his 'dust theory', and I cannot contemplate CAs without thinking of this book. The first pages hooked me utterly. Australia should be proud, a fine author.
Rating:
Summary: Mind Boggling
Review: I'd have to rate this book as one of my all-time favorite SF books. I still freak out a bit if I think too hard about his dust hypothesis. The best thing about this book is that I read it soon after I had read "The Minds I", a collection of essays about AI and human consciousnes. I suspect that Egan has read the same book, since many of the concepts of Permutation City are based on the thought experiements in The Minds I. This is not to say that Egan's book is not original, as the title suggests, the book is a riff or fugue on a number of concepts related to identity and consciousness. Most of his wild extrapolations follow perfect logic if you accept the basic premise that a conscious software entity can be created. The idea that, if such an entity exists, maintaining the software state while shutting down the program, then restarting it later from the same state would be experienced by the entity as instantaneous, then following that a succession of these saved states in any chronological order should be perceived as the same experience is mind bending. Amazon should bundle Permutation City and The Mind's I (and maybe Goedel, Escher, Bach) -- they make a great matched set.
Rating:
Summary: Forced Immortality
Review: If you had a chance to live forever, would you take it? Would it matter if it could only be achieved through removing you from reality? And what if once you had attained immortality, you no longer wanted it? Paul Durham awakes as a Copy of his former self, complete with the knowledge that he is here for a purpose. He tries to leave his new reality only to be thwarted by his own tinkering. And once he has adapted to his new surroundings he is put to work by the version of himself still in real time. Permutation City has an interesting underlying plot that addresses many of the social problems associated with immortality, but it is frequently buried beneath complex explanations of chemistry, physics and the dust theory. It is unfortunately so bogged down with this unnecessary baggage that I quite frequently wanted to put down the book and never pick it back up, and I found myself having to reread sections multiple times just to try and find some kind of understanding of what was being explained. In the end, I felt that the book could have benefited from some shortening and a more complete ending. Unless you are a fan of "hard" cyberpunk full of technical descriptions, or want to learn more about how to sculpt things in a new reality, I'd recommend either skipping portions of the book, or skipping it entirely.
Rating: 
Summary: A view to balance all others...
Review: If you're looking for a Hard Sci-Fi novel that explores the implications of the Strong AI hypothesis to its uttermost limits, then this is it. Permutation City will change the way you think about AI - unless, like some reviewers, you just don't get "Dust Theory". Trust me, if you know anything about AI then you will easily understand Dust Theory (maybe after the second reading, like me). And it has nothing to do with "chain reactions" (that sounds like Chaos Theory, aka the Butterfly Effect - nothing to do with Dust Theory). Basically, Dust Theory is a hypothesis based on materialism - that consciousness arises from purely physical/chemical actions taking place in a brain; that the brain is a Turing machine of some sort; and that therefore any mechanism capable of simulating a Turing machine can support a consciousness. For example, a computer; or a complex system of cogs and chains; or a system of water pipes and gates; or even a swirling mass of dust particles out in space. If they happen to be arranged in a certain fashion they can be held to be making "computations" and therefore, possible support a consciousness. And this arrangement doesn't have to be in consecutive 3D space - it could be any conceivable n-D "slice" through the 4D universe. To understand this further, read the book. Corrections:
"the emergency "bail-out" option, which is required by law to provide the copy with the choice of becoming a f-and-b person"
- read the book. The "bail-out" option that Egan describes does not awaken the copy into f-and-b; it terminates their program. If you don't understand Dust Theory then it is understandable that you wouldn't understand this part. The Editorial Reviews also got this wrong. If you're a proud computer nerd or just vaguely interested in AI then you'll love Permutation City. I agree with the comments regarding characterizations and the contrived ending; Egan's other works are much better in this regard. Thus, the 4 star rating.
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