While it's called Adventure Time, this game doesn't really benefit from having AT title.
First off, if you're buying this game because it is an adventure time game, you're not buying it for the right reason. It has characters from adventure time, and that's about it. The story isn't gone into too deeply. You find yourself thrust into a videogame world. You try to find bmo. All explained in the opening sequence that's pretty much it.
The main premise of a world is 6 levels and a boss. You hack and slash (kind of button mashy at times) through enemies, collecting various enchiridion pages that offer powers. It's worth mentioning that the game will be very easy unless played on the harder difficulty setting. The pages themselves are plentiful, so you can almost never run out.
I feel that this game might have benefited more from a rogue-like procedural generation level structure, rather than having fixed levels. It would have made it more challenging, and it would have given the game a lot of replay value. As it is, the static levels don't do the game any favours.
This game can be played with both controller or a K&M setup. The controls cannot be customized through the menu, but thre are a few "presets" to choose from. Peronally, I found using a controller to be the more logical way to play this, as there are not many keys to be used.
Thr graphics are very good during gameplay, but when you are shown close-ups during cutscenes, the models look very odd. The cutscenes might have benefited from being animated and pre-rendered. There is a fair amont of variance throughout each of the worlds, which is good.
The voice acting in this is limited to that of finn & jakes's cutscenes and some BMO is thrown in there too. Oddly, none of the bosses were given voice acting, despite the fact that they speak in the show. I found this rather odd. The background music for this game is very good. It has a sort of retro gaming feel to it, but it's not fully 8-bit in style.
There are some bugs in this game, but none I found to be game breaking in any way. The game devs included a "return to start" option in the menu, which helps if you get stuck on a floating island in the middle of nowhere. Fun fact: You can actually use this option at any time, even if it is "greyed out".
In short, don't buy this game just because the adventure time label is slapped on it. It is a fun game for a single playthrough, but beyond that it has no replay value, as far as i'm concerned. If you're a fan of roguelikes you probably won't be interested, but it might appeal more to people who want to get in to roguelikes, as this game is about half way there already, if a bit button mashy at times.