Reaper by A. Zavarelli — book slip

Sasha knows Ronan is dangerous. He's an Irish mobster, silent and deadly, and he hasn't spoken to her in two years. Yet, they share a secret that could cost her life if revealed. Ronan, on the other hand, is obsessed with Sasha. He watches her from the shadows, ready to kill anyone who threatens her, but he can't protect her from himself.

Second in the Boston Underworld series.