Black Box by Julie Schumacher

This is a fast, short read, but it is very powerful. The story and the main character (Lena - short for Elena) draw you in immediately. She has an older sister, who has always been erratic, bubbly, moody, fun. The opposite of how Lena is. But they are very close. Then her sister gets so depressed that her parents intern her into a mental health facility. Lena doesn't know if by staying loyal to her sister, she is facilitating her destructive behavior, but she also just wants things to go back to "normal". Very good read for teens, and adults especially parents dealing with a depressed child.