The Progeny (Descendants of the House of Bathory #1) By Tosca Lee

Emily Jacobs is the descendant of a serial killer. Now, she's become the hunted.

She's on a quest that will take her to the secret underground of Europe and the inner circles of three ancient orders--one determined to kill her, one devoted to keeping her alive, and one she must ultimately save.

Filled with adrenaline, romance, and reversals, The Progeny is the present-day saga of a 400-year-old war between the uncanny descendants of "Blood Countess" Elizabeth Bathory, the most prolific female serial killer of all time, and a secret society dedicated to erasing every one of her descendants. It is a story about the search for self filled with centuries-old intrigues against the backdrop of atrocity and hope.