Double-Sided Magic

Levy Michaels deals in antiques and hides what she is. She was born a Legacy, heir to a form of magic the supernatural world outlawed after the Cleanse, a purge in which Legacies tried to make themselves the only species worthy of magic and left a great many bodies behind. Being a Legacy is not a secret you survive having discovered, so Levy has spent her life passing as human.

Then an enchanted dagger disappears from her shop, and she comes to on the floor beside three dead supernaturals with no memory of how they got that way. The investigation belongs to Gareth Reynolds, the calculating head of the Supernatural Guild, and he is exactly the person best positioned to expose her. He also, inconveniently, does not think she did it.

Double-Sided Magic is the first book in McKenzie Hunter's Legacy series, an urban fantasy published in 2016. It runs on a magic system with real rules, a slow-building attraction between Levy and Gareth, and a world where hiding what you are is a full-time job.