Legion of Pride (Sins of the Half Blood #1) by Stephanie Storm:
 
She’s taking the FBI by storm. Even if no one knows about her dark secret.

Graduating at the top of her class at the FBI Academy, Iris Young is on track to make all her dreams come true. Racking up an impressive case closure rate, Iris is so close to getting her dream special agent, the youngest the department has ever seen.

When a serial killer makes Iris’s city his deadly playground, it threatens to unravel everything she has worked so hard to achieve. With bodies and crime scenes popping up all over the city, Iris is tasked with catching the killer and ending his string of gruesome murders. Easy for a superstar achiever like her, right?

Suspecting they are up against an otherworldly being, Iris finds herself in his crosshairs as the killer leaves cryptic messages for her at the scene of his murders. Iris believes she knows exactly why she’s been singled out in the calling cards; the killer knows what she is, a fact she’s worked hard to hide from everyone in her life, including her husband.

With the government demanding answers and the killer’s death count rising, Iris finds herself faced with an impossible feat of catching a murderer while also concealing her darkest secret. When forced to make a choice, will Iris give up everything to protect the city she loves, or will she let the killer run free to protect her secret?

—

Dexter meets Criminal Minds in this psychological urban fantasy series following Iris Young as she’s under pressure to apprehend a serial killer destroying her city. The stakes have never been higher as the killer develops an obsession with Iris, bringing far more attention to her dual nature than she’s ever wanted.