The Face on the Milk Carton by Caroline B. Cooney
This has been on my Recommend List for a long time - it's just never managed to find a slot to sneak into. You don't necessarily have to be a serious teen at all to read this book, though the subject matter is rather serious. Janie sees a young child's face on a milk carton one day and suddenly realizes - that's me! From there, Janie's life seems to spiral beyond her control as she discovers the truth about her parents, her life, and where she really came from. Cooney does a great job capturing the emotion of this story and to this day I still remember all sorts of individual snippets of this book. The same can't be said for all the books I read, that's for sure. Especially since I read this book when I was in 7th grade. There's a second book after this one that's 99% as good, and I later learned Cooney made a few more for this series, but for me, I'm comfortable with how it ended after book 2. Definitely give this one a try. It's not that long, and well worth your time.
Notes from the playlist: "Hole in the Head" by Sugababes