Matt Edward’s story began when he was a high school freshman. After a clinical procedure, he received a prescription for Vicodin. He felt “touched by God” after taking the first pill and was never the same. Shortly before his death, Matt told his mother, “If anything happens to me, my journals will explain everything.” They do.

What I Couldn’t Tell You is a diary of Matt’s life until his death at age 25 from an overdose. Matt paints a self-portrait of a young man who’s intelligent, articulate, and full of dreams, and who wishes...