The Clan of Deception (The Calpa #1.1)

When a powerful magical grimoire is stolen from a clan of witches, Isabella Shadowsoul, a bounty hunter witch, is hired and drawn to an underground auction where the book is being sold. At a local club, she meets up with Grif Nathaira, a handsome man who she learns through a mutual friend has connections with individuals running the auction.
Grif, a snake shifter, is also tracking the thief but for a different purpose. After he enters her life, destiny and duty become tangled with desire and need. Long suppressed feelings emerge that she thought she’d buried deep. He incites her anger, makes her question everything she believes in, and tempts her with the forbidden.

Together they race to find the thief while they fight their feelings to focus on their tasks before they can use the book's power for evil