The adult coloring book craze came as no surprise to us.

We at Super have been known to buy kiddie coloring books to use them as a way to relax. Coloring books and crayons are also among our favorite things to cheer up friends in the hospital.

But these aren’t your little sister’s coloring books. Instead of popular cartoon characters, most adult coloring books feature intricate patterns, fine lines, complex drawings—the better to challenge your shading skills.

(READ: Super shopping list: Coloring tools)

Adult coloring books are flying off the shelves around the world, including the Philippines.

Johanna Basford’s “Secret Garden: An Inky Treasure Hunt and Coloring Book” is number three on Amazon’s bestseller list. Two other adult coloring books are among the top 20 bestsellers: “Adult Coloring Book: Stress Relieving Patterns” and Angie Grace’s “Balance (Angie’s Extreme Stress Menders Volume 1).”

In New York’s Strand Book Store, Emma Farrarons’ “The Mindfulness Coloring Book:

Anti-Stress Art Therapy for Busy People” is number one on the bestseller list.

Even National Book Store’s managing director Xandra-Ramos Padilla is hooked.

“Adult coloring books are a global phenomenon. I, myself, enjoy coloring with my daughter or girl friends. I find it very relaxing. You can be creative with your color combinations. Part of the excitement is choosing which coloring materials to use. We have so many options in National Book Store,” she said.

Here are some of the coloring books available at National Book Store, Powerbooks and Fully Booked.

And we really wish they’d bring in Theo Nicole Lorenz’s “Unicorns are Jerks” coloring book, too.