Crimes of Magic: The Witch's Artifact by Richard L. King
Portland private investigator Rachel Chase lets her landlord, Professor Robert Walker, ride along on a simple case of alleged infidelity with a witch. The case takes a mysterious turn when a magical artifact is stolen from the witch's partner. A subsequent murder takes Rachel and the Professor into the dangerous world of scientific magic where real magicians defy the laws of nature for their own nefarious purposes.
Rachel is an experienced, no nonsense private investigator, but she has never before encountered the criminal use of magic. As she investigates the case, she has to rely on the Professor's research into the scientific basis of magic to help her solve the crimes. Facing the dangers together, a certain chemistry develops between Rachel and the Professor.
A touch of humor, a budding affection, a dose of magic, an element of danger, a bit of action, and a lot of sleuthing combine to make a modern, urban cozy mystery.
This book, Crimes of Magic: The Witch's Artifact, is the first book in the Crimes of Magic series.