I read a bunch of reviews on this game clamouring about the extreme difficulty. They are correct. This game will mess you up. It will defeat you over and over but you will persevere, and when you finally conquer that boss you will rejoice. But remember to not be too happy... there's a bigger and badder boss around the corner! -- The challenges in this game are legendary. At times you will feel like the game has beaten you, but you will not give up.
You need souls for everything in this game. Buying items from merchants, levelling up, reinforcing weapons and armour, and so forth. You earn souls from defeating any kind of enemy (or friend!). The ease of losing all of your hard-earned souls adds a little more difficulty to the game, which some people think is unnecessary, but it adds to the reward you receive from playing the game and being successful. Let's face it, people who negatively review this game are most likely stuck in the Undead Asylum (this is where the tutorial takes place) or Undead Burg (recommended area to begin the game).
The control system is one of the best I have ever experienced in an action/RPG. It is NOT a button-masher. If you passively enter a battle at an early point in the game, you will die. You will lose all of your hard-earned souls. You will feel cheated, but you will not stop playing. There are many rage-inducing moments of the game, but that rage just fuels your desire to succeed.
Okay, the story is a little lacking, but that's what makes it so much more interesting. The extreme mystery mixed with the difficulty is intriguing... you'll find yourself dying over and over again and thinking to yourself, "Why the hell am I even doing this?" -- The story can be pieced together through item descriptions and dialogue from the NPCs (non-player characters), but much is left up to the imagination of the player. Upon completion of the game, I would recommend checking out 'EpicNameBro' on YouTube; his lore series explains a lot that may have been missed on an initial play-through, and it is also quite interesting and humorous. He does a great job mixing information with hilarity whilst being professional.
If I could think of anything negative to say about this game, it would be the frame-rate issues in Blighttown, the questionable camera controls, and being invaded by players that are much more skilled than you. If you are in human-form and concentrating on the game then this can be very annoying. They should have allowed you to remain a human if you are killed by an invader. I can't tell you how much humanity I have wasted... However, you don't stay human very long because eventually the game itself is going to kill you. Humanity is useful for summoning other players or NPCs for boss battles you just can't complete yourself (you can, but you lack DISCIPLINE!), or kindling bonfires (which boosts the amount of Estus Flasks you can carry; estus flasks are used to heal yourself, so pretty useful indeed).
Another flaw with PvP is people that invade and exploit the critical hit method (mainly backstabbing). There is an easy method to combat this: a) DO NOT LOCK-ON TO YOUR TARGET, and b) swing away with RB (right bumper on the controller). Locking-on allows the invader to effortlessly "glitch" behind you and get the easy backstab. Most of these invaders will (very) likely have progressed through the game at a low level, which means they have had access to powerful weapons and upgrades. Basically, one backstab from one of these players will instantly kill you. Swinging at this invader without discourse catches them off guard and can usually score you an easy kill if you are careful enough; it is necessary to keep your shield down when performing a backstab, so they will be much more susceptible to damage.
For the Next D- Souls game, they really need to focus on improving the multiplayer/invading/summoning system.
One final note, PATIENCE IS ESSENTIAL. The angrier you get, the more mistakes you will make. The more mistakes you make, the more souls and humanity you will lose. The more souls and humanity you lose, the harder this game will be. If you are easily angered in other games, I might not recommend this to you. However, that is what others told me. Other games have me scream profanities, but this game... is different. I die countless times, but it just makes me want to win. I expect to die, which may be the proper way to approach it.
When you first look at the back cover of the game case, you see the following words printed in bold and capitalized: PREPARE TO DIE. I couldn't say it better myself. But you should also prepare yourself for an amazing journey.
Dark Souls.