The no-mess thing is what sold me — my son colors the fairy tale pages for a solid 20 minutes while I actually get to sit down. The chunky pen is easy for his 4-year-old hands to grip, and it refills so we're not constantly hunting for replacements.
The water pen is genius — my daughter scribbles all over the fairy tale pages and the colors just bloom, then fade once it dries so she can start over. No ink stains on the couch or her clothes either, which honestly sold me more than the coloring part.
My three-year-old can handle the chunky water pen by herself, which is huge for independent play. We’ve taken it on two car trips and not a single drop has spilled, and the pages are ready to color again within a few minutes.