What is the lesson in Miss Peregrine's Home for Peculiar Children about good and evil?

This is an exceedingly complex question, so I will discuss the roles of good and evil in Jacob’s life as a focal point.
Prior to his grandfather’s death, Jacob lives a monotonous life in Florida where his parents are oblivious to the dangers lurking around them. Jacob’s father dismisses the fantastical stories the grandfather had told Jacob—and Jacob’s father—as lies made up by a man who was never there for his family. Furthermore, his parents think Jacob is losing his sanity when he becomes obsessed with finding out what his grandfather’s cryptic last words really mean.
The evil that Abraham discussed goes beyond the Nazis he escaped as a child. The hollows and wites that seek to devour the peculiar children—Jacob among them—are representative of that evil in the world.
Jacob, being a force for good, defeats the chief wite Golan in this book. This shows that Jacob is able to conquer evil because of his innate goodness. Prior to visiting Cairnholm, Jacob didn’t realize the power he had not only as a peculiar but also as an individual whose actions can actually make an impact on the world. Jacob comes of age over the course of this text because he harnesses his power for good.