Game Changer, the long-awaited book by Matthew Sadler and Natasha Regan, has now appeared. This represents the most thorough inside story about the sensation that is AlphaZero. It includes material by the DeepMind founder Demis Hassabis and by Garry Kasparov, who must be gratified by the authors’ conclusion that DeepMind’s brainchild plays in the style of the 13th world champion — aggressive, sacrificial, seeking the initiative while keeping its own king safe.