Here are three titles I bought (along with a 24-pack of Crayola colored pencils--though I'd recommend a larger variety):
Adult Coloring Book: Stress Relieving Patterns Paperback – March 28, 2015
by Adult Coloring Book Artists (Author)
Detailed Designs and Beautiful Patterns (Sacred Mandala Designs and Patterns Coloring Books for Adults) (Volume 28) Paperback – September 18, 2014
by Lilt Kids Coloring Books (Author)
Balance (Angie's Extreme Stress Menders Volume 1) Paperback – February 22, 2015
by Angie Grace (Author)