Devil Survivor Overclocked is fantastic.
Gameplay:
If any of this sounds overwhelming, don't worry, it really isn't. Plus they do a fantastic job of easing you into it.
There's no crapshoot demon negotiation. To get new demons, you bid on them on the black market, and once you understand how it works, you can win every single auction you enter. Plus you can fuse them to make ideal teams of 3 (one human, two demons). A lot of their various abilities and passive skills can synergize well too, once you know what to look for.
In terms of combat, it's great too. You have your team of modern-day-demon-summoners going around on a tactical map a-la-final fantasy tactics, finding good angles to engage the enemy. Then, when you attack something, it goes into pure turn based combat "skirmish", where each side gets a single turn. However, if you reflect attacks, or hit a weakness or land a critical hit, the character that landed it will gain an "extra turn", allowing them to get a second attack in before the skirmish ends. Plus, there's the added dilemma of who to target. If you kill the team leader (the guy in the middle), the whole enemy team dies. However, the leader gets a defense boost if they have teammates still alive, and you get more money/experience for wiping out entire teams than you get for just nuking the leader.
And finally, there's the Skill Crack system. Early on, you'll gain the ability to pick an enemy skill at the start of each battle (not the skirmishes you have, I'm talking the full tactical battle). If the team you select to "crack" that skill kills the enemy holding that skill, you permanently gain the skill and can equip it to any of your human members, and eventually pass them along to your demons too.
Story:
The story for the first game is FANTASTIC.
Your summer vacation gets dramatically cut short when your cousin (a computer genius) gives you some modified COMPs (they're like a DS in that game), which suddenly spew out demons, as well as a cryptic daily email predicting the future.
The very next morning, you find out that the inner loop of tokyo, where you are staying, has been locked down by the army and they will not hesitate to use lethal force to keep everyone in there and prevent the demons from getting out.
So, you and your band of friends (and whoever else you can convince to join you) are trapped in a locked-down city with no power, little food, and rampaging demons slowly taking over as civilization within the loop quickly degrades into full-on survival insanity. Your only real clues as to how to prevent disasters and death from happening are those daily predictive emails.
Oh, and you're pretty sure that if you don't do something big, everyone in the loop is going to die in 7 days. The clock is ticking, GO.
It's a game where choosing who to spend time with and who to listen to or ally with or even whose life to save can have a tremendous impact on the game. Allies may come and go, endings may be permanently cut off, etc.
And did I mention there are 7 endings and a robust new game plus mode? Because there are.
Devil Survivor Overclocked an excellent game, and you really ought to play it.