Spirit Tracks is the sequel game to The Legend of Zelda: Phantom Hourglass. It was released in 2009 on the Nintendo DS. It's one of the least popular games in the series, but that's kind of a hard thing to measure anyways. It definitely doesn't get the same amount of love a game like Twilight Princess gets, though. Either way, it's my personal favorite!
Here are the most important things you need to know about Spirit Tracks:
1.Trains.
Basically the entire game is centered around trains. Sometimes you might forget that it's about trains, but it is. The main storyline revolves around the disappearance of the Spirit Tracks (WOAH!!! They said the thing!!!), the magical mystical train tracks that act as chains to hold down the demon Malladus so he doesn't destroy the entire world. Throughout the game, you go through dungeons to retrieve the Rail Maps, which recover the Spirit Tracks, blah blah blah it's all very complicated. Read up on the Spirit Tracks lore.
2. Zelda is DEAD.
Well, sort of. She's not dead for good, her body and her spirit just kinda got separated. The royal chancellor, Cole, was secretly evil all along and is also best friends with Malladus. He shoots dark magic of some sort at Zelda, she falls to the ground, and her ghost floats away. But now she can come along on the adventure with you!!! She's almost playable!!! Not really though because Nintendo won't let us be happy.
3. The story is really interesting but no one cares enough to appreciate it :[
I could honestly go on for hours or even days about the Spirit Tracks lore because it's really, really interesting if you just think about it a bit. I think people don't give it enough credit just because silly trains and the toon artstyle and no one likes handheld Zelda. It has just as much depth as any other game from the franchise, dammit! And I love it!!!