Shiver by Maggie Stiefvater

Grace was attacked by wolves when she was just 6 years old. Since then, she's always found wolves fascinating, especially the wolf that saved her all those years ago.

Sam knows Grace should have turned into a wolf when she was 6. He's watched her every winter as a wolf and tries to work up the courage to speak to her in the summer.

Then one of Grace's classmates, Jack, is attacked by wolves and supposedly dies. Sam ends up shot. And Grace soon learns the wolf she sees every winter knows more than he's willing to tell.

This story is told from Grace and Sam's points of view. How the wolves become human or wolf is all part of the story, and Grace and Sam's story is more tragic because of it. A great romance story with paranormal overtones. There's some action thrown in as well, but most of the story focuses on Grace, Sam, and their feelings for each other.

The sequel to this book is Linger.