First things first: this is most definitely not a game for impressionable youths. The main mechanic of the game is that once it reaches midnight, the Dark Hour begins. Everything becomes shrouded in darkness. The electricity stops working and all but a handful of people are transformed into coffins. Then, you have the Shadows. Evil creatures which kill anyone they come across. Usually they are confined to the mysterious Tartarus, but the stronger ones can escape. The only ones able to fight them are the Persona users, who are able to summon alternate personalities by shooting themselves in the head. Seriously. No typo. One of the best stories in a video game, or indeed in any form, it is up to you to find out the secret behind Tartarus and the threat which could kill everyone on the planet.
Sorry, to go on about the plot, but one of the great downsides to this game is that the plot is by far the major selling point. The gameplay itself leaves a lot to be desired and the classic music from the original persona games has been replaced with modern J-Pop. It plays much like any other RPGs, though the weakness system does add a new level of strategy. Outside the dungeon however is a whole other story, playing out much like a visual novel, which I personally felt was a welcome addition to the series.
Essentially, what you're paying for is a visual novel with battles thrown in to keep it from getting stale. If you like that kind of thing, then this is the game for you. If not, then it probably isn't your cup of tea.