This is pure SF at its purest; original, admittedly difficult and challenging, but pushing the boundaries of the genre and rewarding the reader who perseveres.
In the past authors have felt obliged to patronise their readership by providing a certain amount of explanation of the science involved. To be fair to the average readership this is sometimes necessary and indeed Egan provides a glossary at the end of the book which defines some of the terms and concepts explored.
Even so this novel, described by one critic as ‘more science than fiction’, although a brilliant and rewarding piece, is in places very hard work, particularly when Egan goes off into pages of lengthy and eloquent scientific arpeggio.
The basic premise is that toward the end of the 30th century, Humanity has schismed into several forms: the Polises (a polis being a virtual city of digitised human brain structures), Gleisners (similarly digitised humans, but who choose to inhabit physical bodies) and Fleshers (who are physically human but may or may not have genetically engineered their structure). There are also extreme degrees of difference and divergence within these three main groups.
The aftermath of a cosmic disaster forces the polises and the gleisners to send a thousand copies of their populated cities (with copies of the inhabitants) out into the galaxy. There it is discovered – from a vanished Elder Race known as The Transmuters who have left coded messages locked within the structures of neutrons - that a similar collapse is about to occur at the core of the galaxy. One millions of times more powerful than the original disaster; one which will engulf the entire galaxy.
The race is then on to follow in the steps of the Elder Race into another Universe with different physical laws where they will be safe from the aftermath of the core collapse.
The science from here on gets even more complex and is apparently based on the theories and beliefs of contemporary thinking in Physics. Those who know something of Modern Physics and indeed, those who are well acquainted with SF conventions will get far more from this novel than the lay reader.
It has to be said however, that it is to Egan’s credit that he has not been tempted to ‘dumb down’ his writing at all. The breadth of his ideas is breathtaking, beginning with a detailed, very plausible and quite fascinating description of the ‘psychogenesis’ of a digitised personality. Much of the novel is concerned with the subject of individual identity, consciousness and the very nature of ‘self’.
It’s also a novel which poses many questions about our possible future as a designer species, and in so doing, in a kind of Hard SF Dick legacy, questions what it means to be human.