Almost every problem I have with science fiction is represented in this sprawling book—a ton of really interesting ideas poorly served by a rambling and disjointed plot populated by too many hastily drawn characters. I had greatly enjoyed McMullen's earlier book, The Centurion's Empire and was hoping he'd be able to exercise the same control he showed in that book, but this was a bit of a disappointment.
The worldbuilding is quite impressive. Set almost two millennia from now, the world is still recovering from a nuclear winter. In Australia a low-tech civilization putters along, with power resting in the hands of librarians. A new head overlibrarian is elected and brings change, as she ruthlessly builds "The Calculator", a primitive computer using imprisoned people as circuits, and extends a series of communication towers across the various fiefdoms and emirates. The initial exploration of this is quite interesting, but as the overlibrarian's power grows, McMullen starts adding more and more storylines to the mix.
It seems that an ancient sunshade being formed by nanotechnology is threatening to block out the sun and initiate a new Ice Age, unless the overlibrarian can do something. Then there's the barbarian horde being mustered by one of her former protégés—for reasons that are never really clear to me, other than the need to have a big war in the book. Then there's the mysterious force that sweeps across the land intermittently, causing all who aren't tied down to walk due south forever. Then there's a whole genetics subplot. Not to mention an awfully confusing series of romances and affairs, you really do need a scorecard to keep track of everyone.
The ideas are all individually really interesting, it's just that there are too many of them at once and the characters are too flimsy to carry them. Coincidence comes into play all too often, as characters are constantly running into each other, and too many of them are cast from the same obsessive mold and act altogether arbitrarily. It doesn't help that there are abrupt leaps of time in the middle of chapters, out of nowhere will pop up the declaration that five years has passed, for example. Also, the book is badly in need of a map. Geography is an integral part of the plot, and without a map to clarify things, the reader is often literally lost.
I salute the McMullen's imagination for ideas, but this book is just too long and haphazard to properly enjoy. I doubt I'll be seeking out it's sequels, The Miocene Arrow and Eyes of the Calculor.