Ghostlight by Marion Zimmer Bradley
Truth Jourdemayne has long been embarrassed and angry about the fact that her father was Thorne Blackburn: mystic, showman, murderer?
In 1969, when Truth was two years old her mother died during an elaborate magickal ceremony and Thorne vanished. Ever since his infamous shadow has hung over her. Now Truth has found a spellbook that belonged to her father and this leads her to his old home, Shadow's Gate, where her mother died.
Truth is looking for answers and her own identity. But at Shadow's Gate she finds a coven who are followers of Blackburn's magick and they intend to carry out his greatest and most dangerous ceremony in a few weeks. Despite all common sense Truth moves in with them and learns more about her father and herself. Her voyage of self-discovery is both life threatening and soul endangering.
This is a good read albeit one with a gaping flaw. And that flaw is Truth, she is a stupid, self-righteous moron with zero self-preservation skills. She keeps comparing herself to the heroine of a gothic novel as she gets into endless dangerous scrapes. Yet she keeps doing stupid things. Still Truth aside, I enjoyed this tale.