Wicked Fortune by J. Kenner

Matthew Holt built an empire on secrets, a polished billionaire hiding from the shadows of his past. Powerful and focused, he won’t let anyone stand in his way. Least of all a woman. But when Aria Parker steps into his office, he is determined to have her—whatever the cost.
Aria isn’t just any personal assistant. Blaming Matthew for the tragic death of a dear friend, Aria has infiltrated his world, intent on uncovering the truth. But as the heat between them intensifies, their growing attraction becomes just as dangerous as the truth she’s chasing.
The deeper she digs, the more elusive the answers become, until all she knows for certain is how much she craves his touch—no matter the consequences.

With everything on the line, Aria must decide if she can trust the man she came to destroy. Because the more she learns, the more she realizes that Matthew might not be the monster she thought—but the one person who can help her uncover the threat still lurking in the shadows.