Due to me putting 130+ hours into the game, I feel like I have a right to review it.
Compared to other games such as Europa Universalis or any other Grand Strategy game, The Calm & the Storm is pretty simplistic when it comes to gameplay. Diplomacy is simple and combat is relatively easy to learn.
One thing I will mention though, is that the world market is your best friend. if you play as anyone but the U.S USSR or Germany (I'm not sure about the U.K or China) then you will become dependent to the world market. Surprisingly, the same goes to self-sufficient countries if you want to keep a fairly steady income.
That's all I'm going to mention about the game because if you download custom scenarios (which I HIGHLY recommend) then the gameplay, research, resource consumption, world market, etc will change depending on the scenario.
For an example, I downloaded a scenario that let me played as the Holy Roman Empire in 1936, I fought the Nazis, conquered Europe, and fought the USSR and the U.K as a pro-Fascist SuperPower. Yes, Hitler was beaten by Julius Caesar.
I definitely recommend this to anyone who wants to get into Grand Strategy games. This is a good place to start with it's cheap price and its simple gameplay mechanics.