DC: Policeman in Gotham

Marco Vitale wakes up one morning to discover he's been transported from his normal life into Gotham City, specifically, into the body of a version of himself who already exists in this world. He has all the memories of both lives: his original world and this Gotham existence where his father was killed in GCPD crossfire and he became a patrol officer through the department's "blood money" compensation program. Trapped in one of DC Comics' most dangerous cities with a pathetic salary, debts, and no clear way out, he discovers he has some kind of cheat system. During his morning shift babysitting a crime scene in Gotham's East End, he activates one card from his system, selecting what turns out to be a "Higher-Dimensional Construct" ability that makes him immune to reality-warping. The problem? It's a "V1.0 Trial Version," and he has no idea what the other three cards do or how to unlock them. His shift isn't even halfway over, and dispatch is already sending him to handle a domestic violence call. Welcome to Gotham City. Try not to die. — Description from novelcodex.org