Let me put it this way:
Have you ever played the following?
Hard Truck 2
18 Wheels of steel
18 Wheels of steel: American Lon Haul, Convoy, etc..
or a similar game made by 1C Company/SoftLab-Nsk
If you have, they pretty much follow the same line, the only difference being that the most recent game uses (a little) more sophisticated graphics, recent trucks, different cities and some options and details.
If you have no idea what those games were, expect a fully loaded simulator with very good realism, attention to details, a complex system of roads (that include highways and rural roads) and an array of powerful trucks that provide the right sensation of driving a rig and the difficulties that come along.
The cities are not at they're original size, but usually there are landmarks to identify them.
It mostly consists of:
1 - Buying a Rig to start;
2 - Do deliveries, thus earning cash;
3 - Upgrade truck;
4 - Do more of 2;
5 - Upgrade the Rig to it's max;
6 - Even more of 2;
7 - Buy a new truck;
8 - 2 again;
9 - Hire drivers to start a fleet (if that's available in this particular game);
10 - 2 Once more;
11 - Drive other out of the competition and win the game.
They're very fun, if you have the patience because IT IS a SIMULATION! No arcade elements here. So you really have to like simulations to trully enjoy this game.
The road rules apply, truck wear out, (very) long drives trough the country. I've found my self driving for 90min just to get a delivery done.
Of course these games are meant to be played with a steering wheel, 'cause with the keyboard it's a bit exaggerated on the reactions. No fuel economy there either. But it's playable.
Anything else you need to know, just ask!