A man is rescued from a post-apocalyptic Earth by humans from a parallel Earth. The organisation he's recruited into search alternate post-apocalyptic Earths.
Extinction Game (2014) by Gary Gibson...?
When your life is based on lies, how do you hunt down the truth?
Jerry Beche should be dead. Instead, he's rescued from a desolate Earth where he was the last man alive. He's then trained for the toughest conditions imaginable and placed with a crack team of specialists. Every one of them is a survivor, as each withstood the violent ending of their own alternate Earth. And their new specialism? To retrieve weapons and data in missions to other apocalyptic worlds. But what is 'the Authority', the shadowy organization that rescued Beche and his fellow survivors? How does it access other timelines? And why does it need these instruments of death?
As Jerry struggles to obey his new masters, he begins to distrust his new companions. A strange bunch, their motivations are less than clear, and accidents start plaguing their missions. Jerry suspects the Authority is feeding them lies, and team members are spying on him. As a dangerous situation spirals into catastrophe, is there anybody he can trust?