You can start by reading about Eastern Europe and Central Asia.
You cited Cuba and North Korea, so I'd like to draw your attention to other Communist countries, USSR, PRC, Yugoslavia - what they were before communism, what they became after communism and what they are doing now. It's a mix and match, but you won't find enough reasons to doubt the success of communism either.
Communism is insupportable. That whole theory is based on 1 thing: "
control." Take control away and the whole structure will crumble like a deck of cards. Now, the question is, do you like that all your actions, aspirations, your propensity for free thinking, your desire to "earn" more than the usual, longing for "choices" in everything from movies to electronics to cars (how about decadent sports cars) to appliances to unique but very comfortable (let's say upscale) residences to your careers, will be curtailed by the need to harmonize with the rest of the population? Or do you want that after you have worked yourself to death you will not be able to own a piece of land or a Porsche 911 Carrera (if your retirement pay will permit) or a private enterprise or trade stocks in the stock market (for your spare cash)...?
Communism is just another term for dictatorship, this time by the communist majority who will force you to "conform" and divest of your fundamental right to own property/ies.
Re former USSR, Yugoslavia and PRC:
1. what they were before: they were monarchies, not capitalists (with the exception of the PRC which only recently extracted itself from centuries of Emperial rule), certainly not democratic capitalists as how we know it now.
2. what are they after: in case of the former USSR and Yugoslavia, their post-communist systems suffered not because of the inherent unsuitability of capitalism but because structurally these countries were not capitalists. They were not also able to immediately adjust after their abrupt transition since their years of communist (or more accurately socialist) social experiments rendered them unprepared for capitalism. In the case of the PRC however, it was lucky it was governed by a leader with immense foresight, Deng Xiaoping, who saw the structural weakness of the Maoist system (Mao's alleged version of the Marxian communist theory), and who slowly shifted Chinese policies to structurally prepare China for Capitalism. Call China's system now as state-led capitalism yet it is still capitalism.