Mafia is one of the best video games of my recent memory. To put it bluntly it is like Grand Theft Auto 3 set in the 1930s. As the title of the game implies your character will be working for the mafia, running around, and robbing banks, you know the usual mafia jobs.
As for game play its a solid 3rd person shooter, with accurate physics and car handling. The game even goes as far, to measure the fuel in you cars tank and the tank can be punctured by a bullet and drained, or worse you'll get blown up. Stray bullets can also puncture tires, thus making driving significantly more difficult. The graphics are great, and the plot is full of twists and turns.