When you pick it up, you will think "what is this". After 2 hours "I wont put this down".
Once you get the hang of the game, understand how everything works and how all the quests work etc. you find the game addictive. The game goes for ages. I have played 40+ hours and i have barely gotten half of the achievements.
The different guilds add so many missions and each provide different perks. As you play through the game and complete different missions from different guilds you gain access to different items which can help with other guild missions and it almost becomes a chain effect.
You feel a sense of accomplishment after completing a hard mission or getting an awesome item.
Any RPG fan or serious gamer should have this on their shelf.