Punch Drunk - The Erin O'Reilly Mysteries, #15

As long as you're breathing, you're still in the fightErin O'Reilly has been walking a dangerous line. In order to save her lover, smooth-talking gangster and former bomb-maker Morton Carlyle, she's been pretending to be a dirty cop. Her efforts have worked well-too well. Evan O'Malley and his underlings are convinced Erin is a criminal just like them. But that means, by the unwritten code of the underworld, she's now fair game.
The O'Malley family is a tinderbox of hatred, resentment, and ambition. When a botched car bombing fails to kill O'Malley enforcer Mickey Connor, the blast sets the whole thing ablaze. The fearsome ex-boxer is sure Erin and her boyfriend are to blame, and he's not the kind of man to just take a punch. He hits back-hard. A serious error in judgment puts Erin's family on the line, pulling her loved ones into the ring.
With more than one life hanging in the balance, Erin and her K-9 Rolf will need every bit of strength, skill, and courage to face down their deadliest opponent in a fight without rules or referee, where the winner will be the one left standing.