I read Baby Teeth so long ago that I remember it was really well done and I remember being afraid of what Hanna did but that's about all. I wish I had picked up a copy to read the last little bit to refresh me a bit more but I don't think it's an absolute necessity. 

Now Hanna is grown up. She's a phlebotomist (and still likes to inflict pain when she feels like it) and gets married to a man 20 years her senior and becomes a stepmother to a 12 year old. She is trying to not let her past dictate her life now (too much). She writes letters to her younger brother to bounce her ideas and feelings off him. 

There are a few clever twists that really enhance the story as you look back on it. I'm really glad I have this follow up to Baby Teeth a chance.