Two different playable characters, from their two events separated by time that are connected. The story just doesn't get old and your given a lot of variety in your difficulty level so if it ever gets too easy for you, try upping the level and getting around the whole game without being seen once. If you are its game over. I will tell you now that it is possible to complete both chapters of this game on the top difficulty in just two hours, but that's only if you ignore everything and just play through it as fast as you can.
But nothing beats waiting patiently behind a stalk of shelves nervously wondering if the guards will see you. That is until they turn their back and you see your opportunity to nab some dog tags or optionally break his neck. As well as trying to avoid more guards by hanging over the edge of the railings and then dropping down on top of anyone who may wander below you. Optionally you could always be a mad man and run head first into them, shooting your way out after they radio for backup.
If gameplay isn't your main focus though then the graphics are great, they haven't seemed to left out anything from the surroundings. Or if your more a story person then this one will have you wanting more with each new twist and turn uncovered you'll have to finish it just so you get to the end and stop being confused. Though the ending is somewhat of a slight disappointment, slight as in minuscule that most people barely notice it. You'll be left wanting to know more.