Gravity Falls is the best show for younger audiences that I have watched as an adult. It is Twin Peaks for kids and it captured everything I longed to be a part of in my youth.
The show was relatively short-lived, which is, in some ways, a blessing because so many series in every medium overstay their welcome, desperately repurposing plot lines, overusing minor characters, and ultimately fizzling out.
Alex Hirsch created something incredibly special and was able to conclude it in an emotionally effective manner. He is not cranking out supplemental material either, but Lost Legends retains all the charm and style of the show because it was not pawned off on some industry hack with a political axe to grind (which is surprising from modern Disney).
I would happily read or watch a return to Gravity Falls, (Twin Peaks pulled it off with the same creative mind, David Lynch, at the helm), but I am more than satisfied with what is available.