I'm not an Adventure Time fan myself, but I hear it's very boring, and is as basic as dungeon crawlers get. The mechanics are overly simple.
However, the voice acting and cutscenes are meant to be top notch, and a treat for Adventure Time fans. It's also supposed to be canon to the Adventure Time lore, and it apparently has a great twist at the end for Adventure Time fans.
So it sounds like a game that you shouldn't touch, but if you like Adventure Time, maybe watch the cutscenes or an LP for the story details.