It's a brilliant game, the best action RPG I've played for a while. It's challenging and will last you a long time. It took me about three weeks of playing to finally beat it.
Some tips would be to start the game playing as a Noble. As a noble you start with a ring that will slowly regain mana which can really help you at the start of the game. Use weapons with more range such as longswords and spears rather than daggers and gauntlets. Skill up early to be able to use longbows (not crossbows); you will find it very useful at certain points in the game to have a long range weapon.
There are two items in the very first area you should acquire before proceeding any further because they will be useful until the end of the game. They are the 'Cling Ring' and the 'Thief's Ring'. The former will increase your health by a substantial amount while in soul form, which is how you'll spend most of the game. The latter will decrease the radius at which you aggro enemies.
Once you get past the first level of the game play coop with others a lot as a Blue Phantom (this means you join their games rather than them joining yours). You will gain a lot of experience, you'll be able to preview the level before you actually embark into the level yourself (or your own Blue Phantoms), and most importantly there is no risk as a Blue Phantom of losing experience. When you die as a Blue Phantom you simply return to your own world.