Duke by Jessica Gadziala

It meant war.

DUKE:

The relative peace we have known for years was gone in one violent act. Then, among the ever-present and increasingly bloody unknown threat, I met her.
But when passions ignite, complicating an already impossible situation, I am left to wonder if there is a way to overcome the dark and twisted secrets of my past that would allow me to have any kind of future with her.

PENNY:

I was just a normal girl. I swear. One moment, I was just living my usual boring life. The next, I found myself in the middle of some kind of underground war between an outlaw biker gang and some faceless enemy.
Trapped in a whole new world and in ever-increasing close proximity to the tall, strong, long blond-haired, deep blue-eyed biker named Duke, yeah, let’s just say things got even more interesting.
But Duke had secrets.
And when they came into the light, I realized they were the kind that I wasn’t sure I could live with…