This game is incredible, you can adjust the enemies difficulty and train like a madman.
The story start out good, the netherworld king dies and the netherworld is on chaos... and a lot of people wants to take the throne... so the prince arises to take back his rightful throne.
The problem is that at the end the game suffer some twists that turns the story less... cool. Both Laharl and Etna (the supposedly main story characters) will have their participation greatly reduced as the story goes near the end, the game could had take advantage of a more serious storyline while keeping the unusual comic it has.
The game also is quite charming, there are those things called prinnies who are rather pathetic... but somehow those things manages to catch the player attention every time they appear.
The combat system is not innovative, but its cool, much better and fast paced than final fantasy tactics advance, the animations are also much better and the skills have a nice variation, both in range and area of effect/damage, this make them very useful in some situations but can also make them useless in others... its all how well you manage to position yourself and how is the situation going.
Music is nothing really great, its ok, but not much that deserves special attention.
In overall is a good game, if you have nothing to do then get this ame and you will be busy all the day.