White Hot by Ilona Andrews

The Hidden Legacy series by #1 New York Times bestselling author Ilona Andrews continues as Nevada and Rogan navigate a world where magic is the norm...and their relationship burns hot
Nevada Baylor has a unique and secret skill-she knows when people are lying-and she's used that magic (along with plain, hard work) to keep her colorful and close-knit family's detective agency afloat. But her new case pits her against the shadowy forces that almost destroyed the city of Houston once before, bringing Nevada back into contact with Connor "Mad" Rogan.
Rogan is a billionaire Prime-the highest rank of magic user-and as unreadable as ever, despite Nevada's "talent." But there's no hiding the sparks between them. Now that the stakes are even higher, both professionally and personally, and their foes are unimaginably powerful, Rogan and Nevada will find that nothing burns like ice...