Start with high-confidence ya mindfulness & meditation books, then narrow by subgenre or adjacent topics.
Wide Awake
Diana Winston
Zen in the Art of the Sat
Matt Bardin, Susan Fine
Anxiety Relief for Teens
Regine Galanti, PhD
Just As You Are
Michelle Skeen, Kelly Skeen
You Are the Universe
Amy Buetens, Julie Weinstein
Rewire Your Anxious Brain for Teens
Debra Kissen PhD, Ashley D. Kendall PhD
10 Minutes to Better Mental Health
Lee David, Debbie Brewin