The Parisian Codex. Paris on the Edge of Magic, #1

In Paris, even vampires deserve a quiet night. Germain Dupré-a centuries-old PI, connoisseur of fresh blood and solitude-has somehow inherited the world's worst co-owner: Romane Bourgeois, a 19-year-old heiress who's 10% yoga, 90% chaos, and 100% convinced his "adorbs" demonic cat is just "going through a phase". But when Nadine Leroy storms into his crypt-like office with a check and a photo of her missing husband (Robert, an antique dealer who specialized in cursed relics), Germain's peace evaporates.
The case reeks of: A medieval embroidery covered in Celtic knots (his masterpiece, stolen centuries ago). A codex so shady it makes Hell's playbook look wholesome. Zagan, a mysterious entity crammed into a dancer's body, who offers a deal: "Help me burn the codex, and I'll grant your deepest wish. Refuse. and Paris becomes my playground." Between patching doors busted by goons and enduring Romane's forced cheeriness, Germain must: Decrypt why shadowy figures and art collectors would kill for a dusty old book.
Stop Zagan from playing apocalyptic pyromaniac. Hide the truth from Romane-especially about her "kitten". For fans of: The Dresden Files meets Locke & Key in a Paris where the past never dies. it just redecorates Germain's basement.