Imperialism is a managerial strategy game that relies heavily on the management aspect.
Basically, you are the leader of one of seven great powers in a randomly generated world. In addition to these great powers, there are numerous minor powers that play important roles in the game as well.
When you first start the game, you'll probably have two excavators that look for minerals (coal, iron, etc.) in mountains and hills, one farmer to increase the output of fields (and other things) that lie strewn about the countryside, a miner who will turn mineral deposits into mines, and an engineer that is literally the basis of your economy!
Let’s start with the economy. You have things like cotton farms, orchards, cattle herds, and farms to produce resources that will in turn be used to create canned food to keep your workers happy. There are forests that provide wood for your nation, which can be used to create boards for making things like weapons, ships, furniture, etc.
You also have minerals (such as coal) that can be used in steel mills and other buildings to create... well, steel and stuff. However, don't think it's easy to get these precious resources! You need to build rail depots and railways to connect them, and that's where the engineer comes in.
In the "Transport" options tab, you can select the number of resources to transport. Transportation units usually start at around eighteen, so you don't have a lot of room. One of the first things you should look at doing is increasing this via the handy-dandy industry screen.
The first thing you'll notice is that there are tons of buildings on the industry screen! Choices range from your Capitol to a furniture factory, and all of these buildings help the economy. The best thing you can do is get everything running smoothly, but that will take a long time (for the most part). You have things like the Capitol to recruit basic workers that can be turned into soldiers or better civilians (to be used for other things like Engineers). Play around a bit. You can also upgrade many of your factories to increase exports, which you can then sell via the "Trade" tab.
Notice how this is going in a stepping-stone fashion? Now, in the "Trade" tab, we have all the mercantile resources and direct exports created by your colony. While you can't choose the selling price, you can choose the number of things you want to sell, as well as items you want to bid for that come from other nations. You can only bid for items from nations that you have "Trade Consultants/Relations" with, which brings us to the final tab, Diplomacy.
In the "Diplomacy" tab, you'll have things such as information about your nation and a world map, as well as ballot boxes for the "League of Governors" (which in turn decides how well your nation is doing on foreign policy). You can also have policies geared towards other nations (as indicated by the little scrolls tab) and can do things like build embassies, create alliances or trade consultants, declare war or peace, and perhaps even get minor nations to join your empire without war (if they like you)!
To entice nations to like you, you can go into the "Grants" tab, and give them $1,000 grants this turn, or every turn, and so on for $3,000, $5,000 and $10,000. Sadly, lots of times at the start of a game you don't have the money to do these things, and it'll usually take a couple of years to get there...
Every year has four turns: spring, summer, fall, and winter. I’m not sure if turns actually affect your industry (e.g. slows down crops in winter), or if it's just to add more realism to the game rather than going from 1815-1816 in one turn.
Occasionally, new technology will be available that'll let you build railways in new areas, or upgrade your terrain to higher levels for increased output. One of the first technologies you'll want, when it becomes available, is the "Iron Railroads" technology. This lets you build over hills, swamps, and other stuff that usually gets in the way of everything.
One thing I forgot to mention was ports. Ports do the same thing as depots, but they don't need railroad connections, and can really come in handy to quickly transport resources that you need.
Now that it's taken me forever to discuss the economic side of the game, its time to discuss the military side! You can build lots of units in this game; from skirmishers and grenadiers, to cavalry and "man of the lines" (that's a ship). Each unit will help kill your enemies ruthlessly without thought, and especially artillery when attacking enemy cities!
Wars with a minor nation are usually very easy, as they never really take offensive action. Wars with a great power are different. You'll want to fortify every one of your provinces and build fortresses in them for extra measure, but build up an offensive force as well.
One neat thing about this game, is that unlike other games where you need to load your men onto ships to transport them across bodies of water, you can just place a ship where you want to invade and tell your troops to go there (which is extremely handy, because less turns = more conquest)! One weak point about the war part of the game is that you can't invade a nation on the same turn you declare war on them.
Other than that though, Imperialism is a wonderful game and worth a try for anyone who likes the managerial genre. All in all, I rate it a 4. It does have flaws, but it's still fun.