In the decade of technology, the newest craze is surprisingly low-tech. Adult coloring books are infiltrating bookstores and are flying off the shelves just as quick. The first shelf customers see as they walk into Barnes and Noble is full of them, Amazon sells over 5,000 different books, and they’re becoming available on various tablets.

Since children coloring books are far too simple, these books have more intricate designs. They include cityscapes, stained glass patterns, detailed nature scenes, and even illustrations based off of popular books and movies (Harry Potter fans get on this). The most popular one on Amazon is “Secret Garden”, which has been sold over 6 million times worldwide.

So why are these taking the world by storm? For one, they’re therapeutic. In the busy life of an adult, taking a break to sit down and color brings your attention to one specific task and, therefore, focuses your mind. The repetition of filling between the lines automatically triggers a relaxing response. Furthermore, the activity includes both sides of your brain, incorporating both problem solving and fine motor skills.

On top of the mentally beneficial aspects, these adult coloring books are cheap. The average cost is about $5 to $10, making them the go-to Christmas gift this season.

So if the children’s menu at your favorite restaurant isn’t cutting it anymore, or is your distant aunt who you haven’t seen since you were an infant is coming to Christmas this year, think of investing in one or two adult coloring books.