Gemina (The Illuminae Files, #2)

by Amie Kaufman

He smiles at her like he’s not tired at all, like he’s not wearing another man’s blood under his suit, like all he wanted in life was to catch a glimpse of her.

She stands tall in Russo’s tac armor, all kevlar and plasteel. Twenty-four hours ago, she was clad in a Danae Matresco jumpsuit worth the GDP of a small moon. She shed it for the workmanlike WUC maintenance gear, then covered that with her grubby white envirosuit. And now, born from the ashes, she’s a warrior in bloodied black, gun in hand.

The multiverse theory. The idea that for every choice made in our reality, the alternate choice is played out in a different spacetime that exists in parallel to our own.