Blood King. Spirit Seeker, #1

While the Blood King lives, no one is safe. Sybille Esmond never wanted to inherit her family's weird business: summoning spirits of the undead and guiding them to the afterlife. While it pays the bills, dealing with supernatural monsters comes with colossal risks, including becoming undead herself. When tall, dark, and undead Elis Tanner, a reformed member of the soulless ever-after, invades Sybille's life, bringing with him a possessive, disembodied ex-wife, those risks get complicated, and those complications become dangerous. Sybille must aid Elis in confronting his jealous ex while also investigating the Blood King, a beast who refuses to die-by stake or by poison. After a harrowing possession leaves her burned and bruised, Sybille finds herself drawing closer to the tempting Elis, who may be the only one capable of helping her kill the unkillable.
With the Blood King and his legions of undead closing in, she discovers her own life is far from the only thing in jeopardy.