If you haven’t been following the world of adult coloring books, you might think they’re just a bunch of floral designs and hypnotic patterns. If you’re a skeptic, you may even think the whole trend is a bit twisted.

And you’re right–in a good way. Some of the adult coloring books that have hit best-seller lists (and not just niche lists) are edgy, cheeky, and downright naughty. They’ve got everything from goth, pagan, and tattoo art to decorated swear words and paeans to unicorn poop. When creative minds get going, you can expect the unexpected–and it’s no different with adult coloring books.

Unless they live in a restrictive country, book creators don’t need to worry about censorship; many adult coloring books are self-published (of course, there are SOME off-limits topics, but not many). And publishers pick up on edgy books if they think they have commercial value.

Edgy coloring books aren’t new; you can find examples of social commentary going back decades. For instance, Andy Warhol did a coloring book in 1953. And in 1961, The Executive Coloring Book was a satirical, Mad Magazine-like look at the business world. The Gay Coloring Book followed in the early 1960s. (See this brief, fascinating adult coloring book history to for more info on interesting works of the past.)

Today’s books are genre-bending, spanning graphic novels, journals, and adult fiction. Even novelist Chuck Palahniuk, author of Fight Club, which spawned the movie, has penned a book of short fiction for adults complete with coloring pages.

While flowers, fairies, and mandalas still prevail, many grownups aren’t so much embracing their inner child as their inner imp, with parody, satire, and rebellion. And there’s nothing wrong with that. You can color both pansies AND swear words. In these often stressful, angry times, we need both kinds to release tension.

Whatever catches your fancy, coloring books are a place not just to bask in visual pleasure, but to discover a world of ideas.