Prepare to die. A lot.
At the end of Demon's Souls introductory tutorial level, you die. You face a giant boss that shrugs off your attacks and kills you with a single hit. This perfectly encapsulates Demon's Souls. In a word, it is uncompromising. Unlike most games, the enemies in Demon's Souls aren't there for you to kill, they are there to kill you. In that, it is reminiscent of Ninja Gaiden, but it shares few other similarities with contemporary action-adventure games.
At its core, Demon's Souls is a role-playing game. You kill monsters to earn their 'souls', the game's universal currency used for everything from buying and upgrading weapons to increasing your character's stats. You select which world to travel to, five in all, from a central hub where you can upgrade and buy new weapons, level up, learn magic and store items. In this Nexus, you are safe. Everywhere else, you are fair game to the vilest, most vicious enemies you've likely seen in any game since the NES days.
Demon's Souls marries its RPG elements to a combat system that, if anything, is reminiscent of the wildly popular (if you're Japanese) Monster Hunter games. That is to say weapons feel weighty and kind of slow, compared to games like God of War and Ninja Gaiden. There are no elaborate combos to remember, it's just light attack, heavy attack, block, parry and roll (again, don't think Ninja Gaiden, instead, go outside, take a running start, and do your best roll. Roughly like that.) You can also use some magic attacks, if your character is so inclined, or a bow and arrow, but melee is the main focus of combat, and also the most satisfying. You can attack an enemy from the back for a critical hit, resulting in impaling your foe with whatever weapon you're using and kicking him free of it. Timing a parry just right will let you counter-attack, running your enemy through so hard you knock him to the ground and follow through with your weapon. I'm just saying.
At this point, you're probably thinking, "this does not sound like fun!" But the thing is, it's so rarely frustrating. Sure, there are a couple of deaths that you probably didn't see coming, because it's impossible to, but once you know about them, they can be avoided. When you die to an enemy, it's your own fault, and you could've done better. And the next time, you do. Almost every death is a learning experience. Learning to be more careful, learning to block that attack just so, learning that maybe you'll want to use the spear that allows you to block while attacking rather than the big broadsword that leaves your defenses wide open. And the moment you defeat the foe that so completely destroyed you earlier, there is hardly a more satisfying feeling in any game.
The game's stages are also very cleverly designed in that you open up shortcuts as you go, so when you die, you'll save considerable time getting to your corpse. Which is especially useful getting to the bosses, because as you might expect, those will probably also end up killing you a bunch of times. The bosses, at times, rival those from Shadow of the Colossus in size, as you will face giant dragons, a towering knight, a flaming spider and much more.
Luckily, you don't have to face all these challenges alone, for Demon's Souls features a very unique multiplayer system. For starters, as long as your PS3 is connected to PSN, you can see other players running around as white ghosts, in their own world doing their own thing. Also, these other players can leave notes on the ground, warning of impending danger. This can definitely end up saving your life, so your first time through you might want to read most of them. Not only that, but you can also summon other players as Blue Phantoms to help you in your world.
There is, however, a catch, as nothing in Demon's Souls comes free. You see, you can only summon these other players when you are in Body Form. You can attain body form by using a rare item or defeating a boss. The alternative is Soul form, and yes, that is pretty much the default mode in Demon's Souls: death. When in body form, however, other, more malicious players can also invade your world as Black Phantoms to try and kill you. That's right, the only way you can enlist help is by consenting to a form of PvP, where the stakes are the souls you've collected. If you're lucky, you won't get invaded, or you'll get invaded by an incompetent player. Should you be so unlucky as to be invaded by a player who is geared solely with the purpose in mind to destroy other players, well... be prepared to fight. Luckily, the Blue Phantom players you summoned can help you against the invader. I have, on one occasion, fought a single Black Phantom for about 15 minutes before he finally left himself open for a finishing blow, in this case my spear through his back followed by my boot kicking him off a cliffside. It was, in a word, epic.
The relentless nature of the game is compounded by the uniquely solitary feeling you get from it. There is no voice chat, so even when you're in co-op, you never get the comfort of a real human presence with you. There is hardly any music. The environments are eery, desolate and hostile, and at times hauntingly beautiful. Looking from the parapets of the Boletarian castle, you may take heart for a brief moment, before advancing towards the next murderous enemy. Other stages are without the prospect of any hope. In fact they feel designed to crush any feeling of hope you might have had. Precarious cliffsides and narrow walkways over a dark abyss, and a swamp that literally wants to kill you. It's not a technical marvel by today's standards, but in terms of presenting a cohesive atmosphere and some hauntingly beautiful vistas, it's unmatched.
There is quite simply nothing like Demon's Souls available today. There are so many nuances and features this review doesn't even cover, as I could literally write pages about it (check out the wiki - I wrote most of it). It is a game for the hardcore, by the hardcore, clearly created with lots and lots of love, even ff at first it seems that the designers may, in fact, hate you. And in turn, you fall in love with it.
Note: Demon's Souls is slated for a Fall release in the USA, but the Asian versions (minus the Japanese ones) are in full English, so import away.