Agency follows Gibson's earlier The Peripheral, in which the uber-wealthy from 100-odd years into the future entertain themselves with computer generated pre-histories, which nonetheless seem (and are?) very real to those inhabiting them. Agency begins in 2017 San Francisco, in an alternative past, with Clinton in the White House and Britain still in the EU. But nuclear war is imminent, so those in the future use high-tech tools to try to stop it. It's a mind-bending premise, and it requires concentration to keep track of what's going on in each timeline, but as is usual with reading Gibson, it just flows. It's dense with detail, some of it about tech which doesn't exist, but Gibson is so prescient that I wouldn't be surprised if it does soon. Oh, and pandemics and climate change wipe out most of the world's population in the next 100 years. Except for the ultra rich.