It's a free MMORPG, and it's better than most console games! The best free MMORPG out there, i can assure you.
The gameplay is not original, but it does have some unique features. It is based on the leveling-up scheme and once you level up, you can spend earned "skill points" on one of four (sometimes five) characteristics, or evenly spread them. It displays a health meter and if it depletes, then you die. it also has a "mana meter", in which mana is the substance used for spell-casting. the gameplay strikes very simmilar resemblence to the gameplay found in Diablo 2, so if you have played this game, you can get an idea of Mu Online. The point of the game is to level up, become stronger (to wield different armours and weaponry), and be the best you can be. Simple, somewhat unoriginal, but beautifully displayed.
The graphics are really a piece of art. Simply put, it has better graphics than most console games (not just talking about the old ones like N64 or PS1) and it is a very nice piece of eyecandy, especially with the lighting and various nature elements. the only place where the graphics could use some more work is the shadowcasting, but overall its great.
Sound is quite simmilar. Amazing use of nature's winds and the clash of swords and armour put this game's sound rating on top. You can even depect what kind of environment your character is treading on, whether it be the crrunching of leaves or the soft padding-like-sound on pavement.
In conclusion, if you're looking for a good MMORPG without the worries of pay, then you should be looking to Mu Online, not that piece of crap game Runescape. Honestly, that game sucks and it is far more known than Mu Online. Spread the word, and make the world a better place!