From the Steam Page:
I played the beta a bit during the the summer but didn't really spend a lot of time on it, as I was wanting to play the complete game. If you've played any of the previous Port Royale games you'll know a lot of what to expect, but there are some changes. Among the most significant changes is making tactical combat turn-based. It was real time in the previous edition which I didn't like. Turn based ought to give me a fighting chance!Set sail and join the colonial powers of Spain, England, France and the Netherlands in their fight for supremacy of the Caribbean in the 17th century.
In ‘Port Royale 4’ you will take control of a colony as a young and ambitious governor who is eager to learn what it takes to manage and grow his small settlement into a bustling trader city.
Develop production chains connecting multiple islands and create complex trade routes across the Caribbean, covering the ever-growing needs of the respective cities. Make use of the detailed sea map to avoid stormy weather regions, cliffs or shallow waters. Fulfill tasks for your nation’s viceroy, earning more fame to unlock town buildings, ships and more. Conquer the cities of rival nations or hunt down their fleets with a letter of marque while also keeping a keen eye out for pirates and other privateers.
For the first time in the series, naval battles will be turn-based, with up to 8 ships battling at one time and tactical captain maneuvers that can turn the tide in even the most hopeless of situations for a glorious victory.
Another change is to the map. Previously when you went from the large strategic map into a port, the game reloaded with a map that just covered the port area. And to look at the strategic situation you had to select the Caribbean map again. Now the map is seamless, you zoom in to look at a port, zoom out as much as you want to look closely at the local situation or zoom all the way out to see the whole Caribbean at a glance.
There also are more tools and automation for trading. This could be busy work in the last game, keeping track of when to sell and when to buy. Now there are trade "bots" to take away some of the mundane work. There is, to me at least, more of an emphasis on building your mercantile empire.
This is rather a niche game so won't appeal to many people. In fact I thought I'd rather lost interest in these business games but this series and also the Patrician series seem to appeal to my interest in ships and history. I will admit that I'm much more attracted to the game for the merchant aspect than the pirating one.
This also might be helpful for folks to understand the game:
Some more eye candy