Great as a dark expansion to Ocarina of Time, though some problems keep it from beating it's predecessor.
The game starts out with you trying to find "your lost friend" in the Lost Woods. As you are minding your own business on Epona a pair of strange fairies come up and scare you off the horse, knocking you out for a little bit. And while out, a scarecrow kid wearing a strange mask steals your ocarina and horse and leaves you in the woods.
Well, as you guess. Link doesn't take that crap and tried to chase after him. And after a short while, you find him. But before you can strike, the power of the mask turns you into a Deku Scrub, and leaves! Well, with an outcast fairy you try to follow him deeper into the wooded caverns.
But no, it doesnt stop there. The caverns you were in takes you to a strange building, a clock tower. Were you should meet a familiar face. The Happy Mask salesman. After a bit of story, you get sent out of the tower, and into the parallel world of Termina, or more specifically Clock Town. A sleepy place, just trying to set up for the Millenium Festival. One problem though: the moon is going to crash into it in 3 days! Leading to a time travelling adventure in the process, Link must stop the moon and save this land from the destruction of Majora's Mask.
Yep. Sounds a lot more interesting than Ocarina of Time? You bet. Termina is a world shrouded in mystery which helps this game out a lot by making you ask a lot of questions. Where is Navi? How come the people arent panicking? What is Clock Town? How do you stop the moon? And so on.
Anothing thumbs up goes to the main draw: the mask collecting. This isn't the boring running errands in Hyrule. These envolve many sidequests, ranging from short item-based ones, to some that take all the three days to do. But don't worry, you have your trusty Ocarina of Time to warp back. But that comes with some drawbacks: you lose all your rupees unless you put them in the bank, and minor items like arrows and seeds.
Now onto the problems. This game is short compared to OoT, half as short, but it is redeemed by upping the difficulty. Another thing: most of the citizens of Termina are recycled from OoT, leaving not much to be suprised by. And the time travelling can make you feel rushed and doesn't encourage you to explore as much.
But all in all, this game is a great and dark expansion to Ocarina of Time. Which means that if you love that game, you will surely find some great qualities in this one. And for being only $10-$15 used nowadays makes it almost a priority for Legend of Zelda fans. So do yourself a favor and pick it up.