The best truck simulator.
The game itself doesn't have a campaign, while you can consider the game itself a really large campaign. What you do is deliver cargos in different cities of Europe. When the delivery is complete, you get some money. You can use money to buy new tractors and get access to different countries throughout Europe. It features countries such as France, Germany, Italy, spain etc. A big, I think disadvantage to the game is that it doesn't feature Greece. During your progress, you will have to take some rest at various points throughout the world. Also, you will have to refill your fuel tank, since, no engines run without fuel.
The game doesn't have multiplayer.
You can also download mods and install them. This adds extra content to your gameplay experience.