What is the main idea of shiver by Maggie Stiefvater?

The main idea is, a girl named Grace was attacked when she was 11 years old by a large pack of wolves, dragged from her back garden. But one wolf in particular saves her, and she doesn't know why, but she always remembers his eyes. Six years later, she still sees the wolf almost every day in the Winter. But one Winter she walks out onto the porch to find a bleeding boy, who has been grazed by a bullet on his neck. Later she finds out that the boy, Sam, is 'her wolf' as she calls him. It's a love story.