They're no longer just colouring books - now they're "colouring therapy", full of spiritual swirls and intricate patterns that sooth the colourist's inner struggles.
Or they're ironic in some way - a Bill Murray colouring book, or a Tokyo Sexwale colouring books, or a colouring book where you have to colour in the covers of other colouring books. So meta. Many colour.
We miss the days when colouring books were just colouring books, based upon our favourite TV shows, films and celebrities.
Here's a massive gallery of some of history's maddest.
It wasn't the only mental Star Trek colouring book, however.
But then... so is the rest of the book.
Sleep well tonight, everyone.
14 JAW-DROPPINGLY TERRIBLE SELF-PUBLISHED BOOKS
32 BIZARRE AFRICAN MOVIE POSTERS
10 THINGS YOU NEVER KNEW ABOUT BEES