One of the main reason adults outgrow coloring is the simplicity- they’re just too easy to color, too easy to stay between the lines, and that’s no fun. It’s not like adults don’t want to color anymore, it's just not as satisfying as it was when we were kids, and our more advanced minds demand a more challenging coloring book.
Enter Peter Deligdisch’s expert level coloring book Between The Lines, it’s jam packed with intricate line drawings that will test your coloring skills, and when you’re done you have the satisfaction of having created something you can pin up on your refrigerator!
-Via 22 Words