Warning: Don't read this book if all you want is a light-hearted story about teenagers having adventures with magic. Katz doesn't shrink from showing all the truly sick stuff that can happen when people's relationships are unbalanced, and she uses the supernatural False Face mask as a tool to show just what might happen between families if there were such things as magical curses and the power to influence people's wills.
The whole background of magical rituals and practices was extremely interesting to read about, although I don't know enough about the actual False Face Society to know if the book exaggerates or builds on what actually existed. Nevertheless, I've never read a book that combined so much realism with fantasy before! Katz's characters are complex enough to remember and really empathize with.
Anyway, Katz also deals a little with Native American culture-loss and the problems people have in building their own identity apart from their parents (an issue for divorced children, but an even bigger problem for children of two cultures, when to "pick" one parent or way of life is seemingly to reject the other). I would say sometimes there's no good choice, but the characters in False Face do the very best they can to make peace with themselves- enough to make me recommend this book to anyone.