So the game has 230+ nodes in history, in my 6-7 hours of gaming on it I've triggered just under 40...
There are side quests in this game, only one of which that I've encountered thus far was a straight-forward fetch quest (and that was the first one you get to do, so I think it was introductory), most are pretty clever bits where you jump forward or backwards in history to obtain info that will let you prevent events from happening or cause events to happen in order to line things up for the quest. For example, one I did you find a guy's dead body in a cave because he got trapped during a cave-in and (obviously) you can go back in time and try to save him.
Almost all of the side quests reveal information about the main characters and world events so they don't have that same "Why the hell am I killing these rats in your basement?" vibe going on. You can actually make choices in the game that abruptly end it (due to triggering a chain of events leading to tragedy) but you only actually get a 'game over' if you die in battle, any 'dead ends' in history you can jump back in time from. Even when you make a bad choice you learn something (about the world, the characters, the mysteries, etc.) so it is worth it to fuck up history as much as it is to save it.
The battle system is pretty awesome and functions almost like a rapid-paced puzzle game (it is easier to watch than it is to explain, so YouTube that shit). The gist of it is that you and the enemies are each lined up on 3x3 grid and your battle skills have the ability to push, pull, launch, etc. the enemies around the battlefield. You can also change the battle order at whim (but by doing so any characters switched around become vulnerable and take extra damage until their next action). The ultimate goal in battle is to shuffle the enemies around until the are all crammed into one square where you can hit them all at once, which if you manage the turn order well you can completely decimate every enemy on the field in a single combo.
It has a nice quick pace to it, often requires clever thinking, and it is one of the first games to make me feel like I don't need to miser my MP. Because you get more rewards for better clustering/combos I am constantly using all my skills and burning through MP like crazy. Even when I am fighting easy enemies I am still trying to get the highest combo kill I can (and having fun doing it). I'd have to say this is easily the best battle system I've seen in an RPG.
The story is absolutely great, and due to the history manipulating mechanics it all plays out like one big "Choose Your Own Adventure" book. This does have a slight drawback, though, as you do end up having to backtrack through events you've already witnessed. However, you can press 'X' to skip a message window or 'Start' to completely skip the entire dialog/cut scene. This can turn what was 15 minutes of events into 15 seconds and you see enemies on the field before you run into them (and can stun them, turn invisible, or simply evade them) so backtracking is not as agonizing as it otherwise could have been. Also, all the events in history you trigger are recorded (along with notes on them) and you can usually freely jump between major events, both forwards and backwards in time along any of the branching histories.
Overall I am pleased with the game, it got good reviews and I was expecting it to be a good game and I am not disappointed in the least. If you like RPGs and you can find it and you have a 3/DS it is definitely worth it (though I've heard isn't easy to do offline due to the limited copies made).
Anyways, back to the game! EDIT:
This game also has a fucking amazing soundtrack
, especially for a DS game. They worked some serious wizardry with the music, it sounds as good on the DS as it does in the clip I linked to.