I would suggest looking up Wicca and Gardnerian Wicca as that is the tradition that started the book of shadows. Study their rituals and you may can insight into what the shadow benders may be like and help you generate ideas. I would also suggest more character development, maybe it will help you discover your plot.
I almost always embrace cliche and stock. "Book of Shadows" is the exception though. There are SO many horror/fantasy books with a "Book of Shadows" in it. I think there's also a comic series by that name already. -Frank
Imagine if you opened the Book of Shadows and all you got was... Message Deleted. This is weird. Funny, though.