This is fairly easy to read even though the narrator and his friends are 17 and in high school I would give it to any one from 6th grade and up.
Freak, Sunshine and Drip have been friends for at least 9 or ten years. They are alphabets as they call themselves. They have medical diagnoses that keep them out of normal classrooms and on the short bus to special classes. They are regularly harassed and even beaten by a BD student and his gang.
One day the bus drops of Sunshine near her home then Drip and Freak and Sunshine just disappears.
Folks immediately accuse Jason (Freak) of hurting Sunshine. He does not stand up well for himself because of his alphabet. Through repeated questioning, DNA testing, a search, a severe beating in the hands of the bullies, its easy to see how much Freak has grown to love Sunshine, how much he is hurting for his loss and scared for her, and how much adults distrust him and he therefore distrusts them. Jason and Derrick (Drip) know about Sunshine's secret place along the river, her secret stash in her room, her scent (like honeysuckle). They do not know about her greatest secret and greatest secret stash. They know they could not hurt their friend. One FBI Agent who gets to know Jason, who looks past his alphabet earns Jason's trust and learns all the truth he can share. It is with certainty that we also know Jason and Derrick, especially Jason did nothing to hurt Sunshine. The search for Sunshine ends due to money issues and a sense that perhaps she left on her own. Agent Mercer lets Jason in on what he knows. Jason later repays this trust by calling on him for help, which he freely gives. There is a realistic, bitter sweet ending. Sympathetic readers are likely to shed a few tears and learn a little of misperceptions about persons with a wide range of disabilities. JDW