The Smoke in Shadows by Sue Wilder

Nic made one impulsive mistake. She wrote a book about a little-known Roman legend known as the Wolf. An immortal man who appeared every fifty years to lead the armies of Rome. She never expected the book to top the New York Times best-seller list, and she felt safe in her imagination when she wrote the vivid love scenes.
Because the man in those scenes. Was. Not. Real.
But then she realized.
He’s real, Nic.
He’s more than you imagined in those love scenes.
And he’s p!ssed as hell at you.

Darius’ job was simple. Evaluate the enemy. Eliminate the threat. Just keep it clean.
Now she was the enemy.
Nicola Poppa. The girl who wrote a book about his life. His failure, for the world to see.
She was everything he should despise. Destroy.
But she got beneath his skin, made him remember. Made him want what he shouldn’t want… her.
She could be everything he needed… but was she his own personal Judas horse? The one who would destroy him?
Or was she his redemption, and a second chance to get love right?