Book two of the Doomstalker trilogy.
This book follows the talented and ambitious Marika as she rises within the Reugge sisterhood of Silth. As she discovers more about her world, it becomes clear that there is a brewing conflict between the male brotherhoods who are rapidly developing industrial technology, and the sterile sisterhoods of Silth, who use their mental powers for everything from communications to transportation even space travel. The more Marika learns, the more she sees within her grasp, as she lies, kills, manipulates her mentor, and does whatever she needs to, to advance herself, as destruction seems to follow in her wake.
Cook creates an interesting situation here, but the book is nearly wholly focused on Marika who is a completely amoral, unsympathetic and rather unlikable character, devoid of any loyalty or compassion which makes it a little hard to root for her!
This is the second part of the Darkwar trilogy. A young witch rises through the ranks of her sisterhood and tries to unite it with the more technological side of their planet so they can all deal with the winter that is threatening to crush their way of life and their very existence. This is an entertaining series. The first two books especially.