A genuinely moving and brilliantly told story, helped by some interesting design choices and a combat focus.
The setting is one of the most compelling aspects of the game, with technological utopia of Cocoon (small planet in the sky of a larger one no less) serving as the main area for the opening hours of the game. This sets up the tremendous back story to the universe, one that features powerful gods, thier servants and monsters gallore.
Enter Lightening, former solider and sister to Sera, whom Lightening is desperatly searching for as a wave of panic englufs Cocoon. This panic is due to the purge, a mass round up of people possibley tainted by something called Pulse Fal'cie. Lightening manages to find Sera, long with Sera's husband to be Snow, a young boy called Hope, an afro sporting gun man named Sazh and a young girl called Vanille. These people are all tainted by the Pulse Fal'ci to become powerful l'cie, able to use magic and summon powerful creatures to aid them in battle but also are now feared by everyone in Cocoon.
The characters above form your party with one more addition, Fang, who joins later in the game. Each is fully fleshed out, and while some people can find Vanille annoying, none of the main characters are ever over the top (even Sazh, who has a baby chocobo living in his afro), and all have different reasons for going on the quest to rid themselves of the taint of the l'cie.
The story is incrediably poignant at times, and you really get to know each character, thier motives and personality. Of course, this being a JRPG, there are certain attributes inherit to the style, but it has been noticably toned down from previous final fantasy games and XIII is all the better for it.
The game is equal parts traditional Final Fantasy and action adventure, with battles taking place with creatues and enemies that are on the field at all times. These can be avoided if needs be, rarely do you need to unless you are slightly underpowered, which you will find out quickly.
Battles swap to a battle screen as normal, however, Square Enix have made a few changes to the system in this title. You now have an 'Auto Battle' option, which will send your main character (you only control one at a time) off attack enemies with what the computer decides is the best attack/spell. While this can lead to some spamming of one button and makes the battles feel a bit monotous, it is also not the best way to go about them.
The computer always seems to pick the weakest way to attack a given enemy and use that when you hit Auto Battle, so it can make fights much harder in the long run, rather than you cycling through the available attacks and selecting the best one for the job.
Information has suddenly become a big part of the combat too, since you only play one character. The other two characters are controlled by the AI, which is generally pretty great, however it can become useless quick as it will spam ineffectual attacks that can do little to no damage until you use the 'Libra' ability or 'Librascope' items, revealing the weaknesses of enemies and making the AI change tactics and use attacks and spells the enemy is weak to.
Add to this the most satisfying and game changing element of combat, paradigms, and the combat is immense fun. Paradigms are a pre determined combination of jobs for each character and can be switched to on the fly in combat. It is a great system because it means if your party is taking serious damage, you can switch to a paradigm that has one or two medics and one or two damage dealing jobs, allowing you to heal your party while still attacking.
This feeds in to another great combat idea, the stagger system. Every enemy has a stagger bar that fills as you attack it, once full the enemy becomes staggered and your attacks do even more damage. Square Enix has played around with this some too, meaning there are some enemies can are almost invunerable until you stagger them and remove thier armour.
So the combat system is brilliant, but what of the rest of the game? the short answer is, linear. While most RPG's open up thier world relatively early, Final Fantasy XIII funnels you down a narrowly expanding path for most of the game, going so far as to hit you with a tutorial after 25 hours of play. It is this narrow focus that is taken from action adventure games, and surprisingly, it works.
You never feel lost in XIII, and you always have a clear sense of purpose, both in terms of story and the next objective. When the game does finally open up and allow you side missions, this linearity is ever present and means that the side missions really are just that and can be used to bulk up your party for the final battles.
Grinding is a chore that will always be in RPG's in some fashion, and it is present here too, though there are only a few areas that really help with this activity. The plus side is that once you reach the maximum limit of the crystarium (the sphere grid style interface that grants new powers and increases health and strength), you absolutely rip through enemies that for most of the game have been too powerful to even comtemplate taking on.
The most interesting departure from standard RPG tropes however, is the leveling system. Your characters no longer gain levels, the crystarium expands to allow you access to more powerful abilities and you can level up your weapons by using upgrades at the games numerous save points (which double as shops and upgrade stations too) increasing your strength stats and in some cases addition abilities such as filling the action gauge faster, which means you can attack faster.
It makes for a brilliantly slick gameplay experience and one that truely delivers on the feeling of your party slowly growing into thier new found powers and abilities. My personal favourite bit of the whole game though, are the summons, here called Eidolons. Each character gets but one, and each is personal to that character on some level, granted to the player during specific story moments, generally when a character is at thier lowest point mentally, not physically. It is great because it shows that these powerful creatues are choosing to help specific characters and that character alone must tame them before they will bond with them.
Final Fantasy XIII isn't without its problems however. The summons are only useable by one character, and since you only play one character at a time, you have to change your party if you want to experience each Eidolon in the game, it's a small annoyance, but an annoyance nonetheless. Much of the games universe can be missed too, if people are unwilling to read the expansive datalog that fleshes out some of the characters, locations and organisations within it.
The biggest problem however, has also been described as one of it's greatest assets. The linear nature of around 80% of the game means the game will be incredibly divisive, as some will welcome the tight structure and focus on the brilliant story, while Final Fantasy purists will miss the ability to find area's of the world for yourself and discover the secrets there in. It's an interesting problem for Square Enix to have, since the series needs to move forward and has done so, but possibly at the expense of some loyal fans.
Overall, Final Fantasy XIII is a brilliant game. I put around 75 hours into it and enjoyed every second. It is a beautiful game, probably the best looking game on any system today and its fantastic universe, poignant story and great cast of characters combine to make it the best Final Fantasy I have played. It will divide it's audience, but those who stick with it will not be disappointed.