Arcane Wisdome by Chelsea Quinn Yarbro

Lucy Wisdome has a secret. 

In the three years since her mother died, Lucy has tried to live a normal high school life while struggling to keep her mother’s memory alive. When she stumbles upon her mother’s book collection in the attic, she is unprepared for what she finds: books on magic, the occult, and numerology – things her mother never mentioned to her. And the more Lucy reads, the more she discovers that what she never believed possible is now very real. When the group of outcast computer hackers she belongs to finds themselves targeted by something far beyond their abilities, Lucy must confront her own fears and a powerful unknown enemy - or risk losing everything she has left. 

A professional writer for more than forty years, Yarbro has sold over eighty books, more than seventy works of short fiction, and more than three dozen essays, introductions, and reviews. She also composes serious music. Her first professional writing – in 1961-2 – was as a playwright for a now long-defunct children’s theater company. By the mid-60s she had switched to writing stories and hasn’t stopped yet.
     In 1997 the Transylvanian Society of Dracula bestowed a literary knighthood on Yarbro, and in 2003 the World Horror Association presented her with a Grand Master award. In 2006 the International Horror Guild enrolled her among their Living Legends, the first woman to be so honored; the Horror Writers Association gave her a Life Achievement Award in 2009. 
     A skeptical occultist for forty years, she has studied everything from alchemy to zoomancy, and in the late 1970s worked occasionally as a professional tarot card reader and palmist at the Magic Cellar in San Francisco.
     Divorced, she lives in the San Francisco Bay Area – with two cats: the irrepressible Butterscotch and Crumpet, the Gang of Two. When not busy writing, she enjoys the symphony or opera.