Beautiful Creatures Theme of Good vs. Evil

You might think you can replace Light and Dark with Good and Evil and call it a day. After all, the Dark Casters seem to cause most of the trouble, while the Light Casters are always fighting against it. But Beautiful Creatures makes it a little more complicated than that. For one thing, there's Macon. He's a Dark creature, a Lilum. Born to be evil, right? But he fights against his nature every day. Then there's Ridley, who doesn't seem 100% bad. And if she isn't all evil, who's to say that Sarafine, Larkin, or any other Dark Caster doesn't have a good streak, too? Are good and evil ever really that black and white?

1. If Lena were Claimed by The Book of Moons, would she have gone Dark or Light? What makes you say that?
2. Is Ridley all bad? Did your opinion of her change throughout the course of the book?
3. Which characters choose to be good or evil, and which were just born that way?