Start with high-confidence therapy for kids & teens books, then narrow by subgenre or adjacent topics.
Breaking Free of Child Anxiety and OCD
Lebowitz, Eli R. Lebowitz
Freeing Your Child From Anxiety, Revised and Updated Edition
Tamar E. Chansky Ph.D., Tamar E. Chansky
1-2-3 Magic
Thomas Phelan PhD, Thomas W. Phelan
Stuff That's Loud
Ben Sedley PhD, Lisa W. Coyne PhD