Stiefvater writes in the author's note at the beginning of the story:
"As I wrote the hot-cold relationship of two people who took turns being the sinner and the sin, I puzzled out how a place like L.A could both destroy a person and build them into something impossible and new... It's also despite the shape-shifting, the truest novel I've written. I hope that those who don't need the truth in it will only see the werewolf and I hope that those who do need the truth will see only the human."When I first read these lines, I couldn't take it seriously but in many ways it's true. Sinner is about two characters who aren't perfect and are incredibly flawed yet still manage to find satisfaction and happiness. Does that mean that I need to see the truth? Haha, maybe.