The coloring craze has indeed ignited among adults and judging by the sales of adult coloring books in the last few months, it has become one of the trendiest things grown-ups do for relaxation. Sometimes, adults share their books with their kids for family bonding activities, especially when the children like the more elaborately detailed drawings for grown-ups. After all, coloring is a kid's activity. However, there are some book releases that take "adult" coloring quite literally.

"Color My Boobs: A Titillating Coloring Book for Adults"

It's a fun and funny gift gag for adults and reviewers from users at Amazon have said that they've enjoyed coloring this book's pages. In fact, it has mostly received five-star ratings. However, this is the type of book you shouldn't be sharing with a 5-year-old just yet (unless you're ready to answer some awkward questions). Let the children stick with coloring Hello Kitty and bunny drawings for a few more years.

"Babes and Bongs Coloring Book! 16 Pages of Adult Marijuana Coloring Fun"

A handmade adult coloring book released via Etsy is filled with naked women clutching "waterpipes, hookahs and handpipes." While there are no "nip slips or explicit nudity" in the drawings, the theme of the book is definitely for adults only. Only color this book when the kids are asleep and maybe keep it sealed in an envelope inside a drawer when not in use.

"The Fetish Coloring Book"

The book is not for kids under 18! It's also not the type of book to bring to work to show your co-workers as there are "bizarre and kinky fetishes of all kinds, depicted in clear, bold lines." It's most definitely NSFW. It even says so on its official site.

"Gangsta Rap Coloring Book"

One Amazon review says the book is a "great conversation piece," but it's not kind of conversation you'd like to have with your kids. The book contains adult language, curse words and sexual undertones alongside graphic drawings. Think about a hiding spot before purchasing this if you have children in the house.

"Scary Clowns"

Even grown-ups still get scared of clowns, so it's a wonder who would ever want to have this coloring book in their collection. However, the idea behind "Scary Clowns" is to "demystify the strange phobia" called coulrophobia, according to Barnes and Noble. Purchase at your own risk.

To learn more about coulrophobia, click HERE. And for more grown-up coloring book ideas, check out this article about popular books or this article about hosting your own coloring party!