Sarah Funderburk turned her phone on silent, closed her laptop, poured herself a glass of Pinot Noir and relaxed - with a coloring book.

As Funderburk colored intricate patterns, creating a mosaic of soft blues, pinks, purples, the 27-year-old woman rediscovered the pleasure of coloring inside the lines.

“I hadn’t realized two hours had passed,” said Funderburk who lives in Atlanta. “My hand started cramping from so much coloring.”

Coloring books for adults have become wildly popular as grown ups seize on the therapeutic benefits of this simple form of artistic expression. Adult coloring books provide an easy creative outlet, a simple way for busy adults to unwind — and unplug.

Don’t expect princesses, superheroes or simple shapes and designs. Instead, this genre of coloring books feature intricate designs and swirling paisleys. Several also feature mandalas, a ritual symbol in Buddhism and Hinduism that represent the universe.

Some adult coloring books have climbed their way up Amazon’s bestselling books. “Adult Coloring Book: Stress Relieving Patterns” ($13.99; PCG Publishing Group) hovers around Amazon’s No. 10 on the bestselling list. Other adult coloring books in the top 25 include the stunningly beautiful pen-and-ink illustrations of “Secret Garden.” ($15.95; King, Laurence Publishing)

Decatur, Ga.-based art therapist Susanne Fincher, who has published five adult coloring books, including her most recent pocket sized one, “The Mini Mandala Coloring Book” ($9.95; Shambhala), said coloring books can be calming, relieve stress and enliven your mood. Coloring books for grown ups also provide an easy entry point for those seeking a creative activity. About four years ago, Fincher found herself coloring pages for comfort while in a hospital room with a gravely ill family member.

“I remember the coloring book – you have some control and you don’t have to decide what to draw. You can enter into an already created structure and it can be soothing,” she said. “It can be your own private space, like a protected bubble.”

Fincher said she has given her clients one of her mandala coloring books for homework between sessions. The simple act of using hands to color pages can be a good way to keep the hands busy instead of doing things like overeating or smoking etc. (To download one of her mandalas for free go to http://creatingmandalas.com/mandalas-for-download).

Meanwhile, Amanda Bennett, mom to four kids between the ages of 7 and 17, has been a life-long fan of coloring books and has colored her fair share of Hello Kitty ones with her kids. And then, a few months ago, she discovered coloring books designed for grown ups – books with cats, paisleys, mandalas. Not only did she quickly develop an affinity for this adult variety, she decided to introduce them to residents at Campbell-Stone Sandy Springs, an independent living retirement community, where she works as an administrative assistant. The coloring books were an immediate hit with seniors, and residents have asked for monthly “Coloring & Cocktails,” she said.

At home, the the family continues to color together. But now everyone, including the 7-year-old prefers the intricate patterns of adult coloring books.

“Coloring – it chills everyone out” said Bennett of Decatur. “You can get lost in coloring and with the mandalas, there is this repetitive pattern, and it’s a Zen-like experience. I am not a creative person but when I color, I feel creative.”

And Funderburk who admits to initially being skeptical of the adult coloring craze, is now completely on board. Sitting at the kitchen table, the PR executive focused on slowly coloring pages of the “Adult Coloring Book,” and all of her other thoughts – her to-do list, deadlines, work stress – fade.

Whether working, driving, checking Facebook, we rarely give themselves a mental break. In the past, we may have checked out while taking an elevator or waiting in line whereas today, we peruse our smartphones.

“I was so focused on coloring between the lines, I wasn’t thinking about anything else,” said Funderburk who is co-owner of the pr firm SPR Atlanta. “It was very nice.”