The Bunker, book 2
Joshua Hale Fialkov et Joe Infurnari2015

A bomb tore a chunk out of San Francisco. Daniel began his job at Aspire, following in his father's footsteps. Will the apocalypse keep happening? Or will something trigger a change in the future? A future where Grady Potts wields his power as president to his advantage. Where Daniel has locked himself away, desperately seeking a cure for the virus. Where Heidi and Billy are criminals. Where Natasha is forced to help Grady find a way to travel into the past…

…but for what purpose? To help change the future? Or to preserve it?