I first read this book several years ago and have reread it since. Periodically, I dip into it and reread some of my favorite parts.
The most interesting character in this book is Kate Hamilton, a very intellectually gifted pastor's daughter who is deeply prejudiced against Catholics. She is also a very private, reserved person. Due to her intellectual bent and her private nature, she has acquired a reputation for being cold-hearted. In some ways, she's imprisoned by her prejudice, which itself is rooted in understandable fear, the cause of which is revealed fairly late in the book. Her father has shaped and reinforced her prejudice. In the course of the novel, Kate is fundamentally changed (for the better) by what seem to be the first meaningful friendships of her life. Three people are particularly instrumental in this change: (a)an old Catholic priest who is her literature professor and helps prepare her for grad school, (b) Deirdre McAvoy, a young woman who pursues Kate's friendship and (c) Jack, a man in his mid-twenties who is preparing to be a priest. Finally, she comes to realize (slowly at first, then in one fell swoop) that the fellow student whom she's almost worshipped has some pretty serious flaws; as he becomes more radical, she starts to see what he's really like and it's not a pretty picture.
Gibson does a great job of conveying the inner lives of her characters. The 3 characters mentioned above (Deirdre, Jack and Kate) all face major turning points in their lives. Here, I'll focus on Kate. Kate has to come to grips with her past and with her father's hold over her. She starts to see the value of other people's perspectives on faith. I think it's fair to say that at the beginning of the novel, Kate lacks a spiritual connection to God; her faith is highly intellectualized. That's not necessarily a bad thing, but focusing almost exclusively on theological doctrine can be a way of avoiding a deep spiritual relationship with the divine. Finally, Kate is awakened to her own unacknowledged romantic love for a fellow student (not the jerk whom she had fantasies of marrying).