One of the best Mario games around.
The game starts off fairly easily, with a whole lot of tutorials. These can be skipped, however, but you shouldn't if you haven't played another mario RPG before. It teaches you the basics of controlling the brothers in battle, from how to attack, to knowing when to pump in some extra damage, and how to counter attack enemies. Even though its so easy to learn, the combat is quite deep - there are a huge variety of cool attacks, such as shell kicking, obese Luigi throwing, and a lot more.
Even better, there's twice the variety for the combat when you get to the Bowser levels. You actually spend more time as Bowser than Mario and Luigi. Bowser's attacks are much more powerful - his punch can literally take the heads off some enemies, and his fire breath can take out anything in his way. His special attacks involve summoning huge piles of his minions, ranging from goombas to shy guys. And when you use one, you are met with a brief touch screen minigame, which influences the strength of your attack.
But this game isn't all combat. There are a huge number of dungeons, featuring some difficult, if a little strange, puzzles. You trampoline your way through Bowser's leg muscles, hammer bits of muscle sticking out of him, give him toothaches, and see thorugh him with an x-ray. Though the puzzles and minigames are fun, something a little more challenging would be appreciated.
Overall, awesome game, almost a must buy for anyone who enjoys a solid RPG.