It is related and some of the characters were in the first book in the series, No Easy Hope. It is more of a supplemental reading to the series.During the Outbreak, like billions of others, a man finds himself infected with the Phage. Desperate to spare his family from watching him become a walking nightmare, he flees. Soon after, he is dead. Two years later, he wakes up. Not in the afterlife, but in his own body. Trapped, unable to control the monster that carries him, and forced to witness the horror of its existence. A hundred miles away, Sergeant Ethan Thompson thinks he has seen the worst the apocalypse has to offer. He is wrong. Following the trail of a dying madman, he will embark on a journey of vengeance that will test the limits of his sanity. Along the way, he will learn that there is no justice at the end of the world. There is only the living and the dead, and in between, there is The Passenger.

    

    A devastating bioweapon will change the face and fate of humanity as we know it. Captain Dominic Holland leads a crew of skilled covert operatives and scientific personnel aboard a clandestine ship dedicated to fighting chemical and biological warfare. Their missions have taken them across the world to combat sinister plots and dangerous adversaries. But their next assignment is more dangerous than any they faced before. Far off the eastern coast of the United States, intelligence officers discover a covert laboratory on an abandoned oil rig with unspeakable horrors. Twisted creatures wash ashore across the country. Hospitals are overrun by patients suffering from an incurable disease with terrifying symptoms. Dom and his team may be the only ones equipped to find out why. They embark on a globe-trotting race to unravel the apocalyptic mystery behind the bioweapon destroying civilization. But will their efforts be enough to turn the tide—or is humanity’s fate already sealed?