It's kind of like marmalade... you'll either love it or hate it
Right, you start off as a begginer on the beginner island, there you learn the basics of the game and is quite useful, here you get the chance to get some equipment and money before jumping into the real game. Soon after you get to choose which class you want to be: Mage, Bowman, Warrior or Bandit. Mage tends to be the most populer due to the fact you only need to be lvl 8 to get the job rather than lvl 10 for all the other classes. All classes get their own equipment which can only be worn by their class and skill trees which you put skill points into every level, what you expect from an RPG really.
Right I'll talk about gameplay since this is the bit that will either make it or break it for you. The best way to describe it is... interesting. Side scrolling MMORPG, don't see those everyday and is quite refreshing from point and click MMOs that seem to be everywhere. You move using the arrow keys and jump by pressing alt and attack with ctrl. The combat is real time and it is quite like a hack n slash because you'll spend most of your time likely pressing ctrl. Insert, home, page up, delete, end and page down are used as quick keys which you set skills or potions or whatever to. A lot of fighting is going to be against a group of monsters and on platforms some good moving and jumping are required. Evertime you get hit or you hit a monster you suffer 'knocback' and are stunned for a second... if you don't try and stay away from the edge of a platform you'll useually end up being knocked off sometimes resulting in fall damage and having to climb back up, some maps are extremly high up and there have been occasions Iv'e been knocked from the top and fell right down to the bottom so there is quite a tactical sense involved in placing yourslef in good positions for fights and moving and jumping about using things like ladders and ropes to your advantage (most monsters can't jump high enough to hit you on them but you can't attack from them either) to get out of the way or using them to jump over monsters to hit them in the back.
It's typical HP and MP (though some of the high end spells need special rocks to be able to cast spells) and gaining exp from quests and monsters to level up and one note: Leveling can take a good while, you really have to put a lot of effort into training to level which can be a good or bad thing (again this is something that may make it or break it for you) but knowing your characters limitsand strengths can help you decide what you should be training against as you have to balance time with amount of exp your going to gain, also taking what sort of loot you get into consideration.
Quests. The quests are useually quite simple, mostly collect X number of items, kill X number of monsters or deliver an iten to some other npc. Quests are useful though, they give you more of a reason to kill loads of monsters than just leveling up as useually completing quests give you access to more (also depending on your lvl) and the rewards can be useful. Tough, one quest I'm currently on requires me to go to loads of places doing different jobs for people in like a chain of 'favours' to get the single item I need. Not to mention having to fight in the 'dungeon' which is where a lot of the games stronger monsters lurk.
Like most online games you can talk, trade ect with other people and become friends and join guilds (very expensive to make) though one dissapointment is that the friends list can only hold 20 people and you have to pay an npc game money (called mesos) to increase the size and it becomes extremely expensive somtimes meaning you have to pick which people you want in your list. You also have fame which people can lower or raise so for example you might help someone with a quest or help them lvl up or get money for a weapon and they might raise your fame for you os people can see how famous you are when they check your profile.
Ok graphics. It's 2D but... very nice, I would much rather it be 2D and keep this quality or graphics than make it 3D and it be runescape looking. It is a very colourful game and the backdrops and settings have quite a variety for the different places you can visit, ranging from urban settings, canyons, lush forests and fields and some of the more darker places like the swamps and underground caverns of the dungeon.
The music is very nice, fit's the game brilliantly.
Overall it has good value (considering the fact it's free to play :P) and is worth a look at at least because it is quite a hate it or love it game. One of the downsides would definatly be that there's no PvP but who knows it might get added! But Maple Story is definatly worth a shot at and is quite a laugh fighting crowds of mosnters with other players and exploring some of the more dangerous parts of the game (can be quite tense when your'e lost in the island dungeon with little HP and higher level than me monsters running around everywhere... that was fun trying to escape :P).
Oh and if anyone needs a hand in the game or whatever my character is 'LegendaryLew' just give me a shout ; )