Key of Knowledge - Nora Roberts

What happens when the very gods depend on mortals for help? That's what three very different young women find out when they are invited to Warrior's Peak.
To librarian Dana Steele, books and the knowledge they hold are the key to contentment. But now that search for knowledge must include the second key needed to release three souls held captive by an evil god. In each generation three are chosen who have the power to release them - if they dare accept a challenge that could promise them great riches but also grave danger...
And now it is Dana's turn.
She won't be alone, for she's formed fast friendships with two very different women. But she can't allow herself to be distracted by the return of the man who broke her heart so long ago, for a danger beyond anyone's imagination is determined to keep her from completing her quest.