Angel Cafe by Jill Morrow.

Angel Cafe is that strange sort of book that's marketed as a paranormal, but more at home on the shelf next to the Frank Peretti's of the writing world. The plot circles around a lawyer with a dead fiancee, and the brand new New Age eating establishment that offers table readings. Several characters are drawn into the personality cult of the local medium, who's channeling something otherworldly and rather demonic. Something that wants Kat, of course. Good creepy fun, if a bit overly religious for my tastes.