Sapphire Flames by Ilona Andrews

In a world where magic is the key to power and wealth, Catalina Baylor is a Prime, the highest rank of magic user, and the Head of her House. Catalina has always been afraid to use her unique powers, but when her friend’s mother and sister are murdered, Catalina risks her reputation and safety to unravel the mystery.

But behind the scenes powerful forces are at work, and one of them is Alessandro Sagredo, the Italian Prime who was once Catalina’s teenage crush. Dangerous and unpredictable, Alessandro’s true motives are unclear, but he’s drawn to Catalina like a moth to a flame.

To help her friend, Catalina must test the limits of her extraordinary powers, but doing so may cost her both her House–and her heart.