Scalzi’s Lock In introduced the brutal, riveting game of Hilketa, in which players wield swords and hammers to try to decapitate each other. The violence is real, but the players are “threeps,” robot-like bodies controlled by people immobilized with Haden’s Syndrome, so no one actually gets hurt. At least, that’s the idea. The sequel opens with the shocking death of a star player, and as a pair of investigators piece together what happened, they reveal the dark side of the near future’s most popular game, a side where the rules are still being decided. One of the major names in science fiction, Scalzi, award-winning author of Old Man’s War and Redshirts, deftly combines a high-tech speculative landscape with the snappy dialogue and fast pace of a police procedural.