Reynolds always has big ideas. In this case, Earth has been devastated by rogue nanotechnology, humanity is divided between preservations Thresholders around Earth and exotic nano-using radical Slashers deep in the system, and is on the brink of war over access to Earth and the galactic hypernetwork, which mostly leads to empty stars and dead planets. But somewhere, out there, is an Earth where it is 1959, World War II did not happen, and an American tourist in Paris has been murdered. And when these two words meet--we'll, I'm not going to spoil the book, but I stayed up all night reading it.