Taking on the role of Altair, a disgraced assassin who disrespects his elders, you are set the task, to restore your good name, of killing a sequence of progressivley evil persons in various parts of the Holy Land; Damascus, Jerusalem and Acre three huge cities.
As a spectacle, Assassin's Creed is convincing and much has been made of the crowd technology. This shows itself in such ways as when you do something which attracts attention to yourself when a crowd of onlookers questions your sanity. The dense crowds do not present an obstacle and after a few minutes you're weaving through and around at a zapping rate, using your "gentle push" button to brush through without causing a confrontation, or dodging them completely by climbing and jumping. Occasionally you do alert the guards, whether by knocking people over or doing something suspicious within their line of sight, or by attacking them and so giving them reason to chase.
The game is long and the story full of slowly unfolding complexities, too long to describe here, but it's all very well done and mostly coherent. A good deal, though not too much time, is spent on essential intelligence gathering by eavesdropping on conversations, pick-pocketing messengers, or interrogating and tracking down informers.
The controls are peculiar, but work very well. The graphics steal the scene; thanks to a clever use of light and shade effects making them almost unbelievably good. Some of the acrobatic, free running effects are also outstanding with running up walls and darting across rooftops.
Perhaps almost the perfect blend of combat mechanics and animation the physical contact is near perfect and with many and varied movements, specially in swordpaly. There are the usual minor problems but mainly the end of the game does not live up to be the surprising event that was promised; you can see it cominga mile away, but I'll let you have the pleasure pf discovering this for yourself. A good, long and complex game but there are better out there.