The Great War is over and humans have spread across the solar system, but mathematician Alex Ligon’s complex computer model has just predicted that humanity is inexplicably doomed within a century. At the same time, scientist Milly Wu has identified what appears to be an extraterrestrial signal, and the idiosyncratic genius Bat searches for weapons from the Great War to add to his collection, finding much more than he bargained for. Their stories and others are intertwined in this tightly plotted and thoroughly engaging follow-up to Sheffield’s Cold as Ice. Nebula Award winner Sheffield distinguishes himself as a writer of intelligence, humor, and a pleasing balance of hard science and interesting, engaging characters. Fans will be particularly delighted to renew their acquaintance with Bat, but readers new to Sheffield’s work should take the plunge enthusiastically — this novel easily and gracefully stands alone as a story of people, science, and the puzzles that both can produce