In the Flesh — K.D. Grace

When Susan Innes comes to visit her friend, Annie Rivers, in Chapel House, the deconsecrated church that Annie is renovating into a home, she discovers her outgoing friend changed, reclusive, secretive, and completely enthralled by a mysterious lover, whose presence is always felt, but never seen, a lover whom she claims is god. As her holiday turns into a nightmare, Susan must come to grips with the fact that her friend's lover is neither imaginary nor is he human, and even worse, he's turned his wandering eye on Susan, and he won't be denied his prize. If Susan is to fight an inhuman stalker intent on having her as his own, she'll need a little inhuman help.