I really enjoyed "Prisoners of Geography" by Tim Marshall. It's a great introduction to modern-day geopolitics, which I was terribly in need of. The overall thesis is that so much of geopolitics comes down to simple geography.
The good soils, waterways, and climate of France, Germany, and England help to explain their consistent hold on power. The US is not going to decline, as we always feel inclined to say, because we are in just about the most fortunate geographic position a country could ask for. Brazil will never be a major international power, despite its size, because of its jungles, poor soil, and un-ideal waterways. Russia is about to make a big play in the arctic to obtain fossil fuels. This is made possible partly because of technology (ice-breaking ships) and largely because of increasingly navigable waterways due to climate change. The great powers of China and India have long been at peace largely because they're separated by the Himalayas, and the Chinese occupation of Tibet was carried out largely to ensure this. Africa is a mess for a hundred reasons (colonial legacies for starters), but geography may be the central.
It's not always geography; political systems can hold countries back, too. The author writes that Argentina is blessed with good geography, and Argentinians could have a standard of living on par with Europeans if it wasn’t for lousy politics.
A hypothetical: What are the countries that have been blessed with good geography, but bungled it? On the other hand, which countries did the most with the least?