The Family Demon. The Toby Le Tocq Mysteries, #2

In Philip Brian Hall's second Toby Le Tocq novel, the reincarnation of Solomon looks into the disturbing case of his business partner's niece. Seven successive boyfriends have died suddenly, the most recent on their wedding night. After a nervous breakdown, the young woman is confined to a mental hospital. A number of seemingly-ordinary local residents, led by a powerful witch, take violent exception to Toby's investigations, and before long he finds himself framed for murder.
Along with his allies Judith and Asa, Toby plunges into the frightening shadow world of vengeful demons and their human acolytes.