The game is set (at least at first) in Castle Wolfenstein during World War II. You play as a captured American soldier who manages to escape from his cell. You traverse different floors (levels) in order to escape. The game is corridor based, and maze like, and features lots and lots of Nazi imagery. There are numourous portraits of Hitler about the levels, and lots of Swaztikas, so gives the impression of being in an evil place, though less so than the excellent space setting of Doom.There are not many enemy types - Aryan Soldiers, German Shepards, and a few others, and not many weapon types (a knife, a pistol, a machine gun, and a gatling gun is all). Many of the levels are quite sparse, and all enemies let out a warning sign before attacking by shouting at you in German making it easy to get the first hit in.
The game has 6 different chapters, each with 9 or 10 levels, and at 400 Microsoft points this has real value for money. It's only really on the 6th chapter that enemies become really numerous, but each chapter features great bosses. I mean, at the end of the 3rd chapter you get to fight Hitler! (wearing a giant robot suit).
A great game to see where the roots of the first person shooter started.