Autism spectrum disorder (ASD or simply autism) is a mysterious disability. Doctors don't know what causes it, it's difficult to diagnose, there's no cure, and there's no universal treatment. Even though more people are diagnosed with autism today than ever before, it's hard for many people to understand why people on the spectrum think and behave the way they do. This book serves as a guide to help teens understand the signs and symptoms of ASD, how ASD is diagnosed and treated, and how knowing someone with ASD can change their lives.