Strongly recommended for fans of tactical combat!
Other reviews have explained in detail the setting and the mechanics of the game, so I will not repeat that. This is just my subjective opinion of the game.
While this is not a random or procedurally generated game, where you could get endless replay value, it is intriguing enough that I have replayed the story a couple of times, making somewhat different decisions within the relatively linear story. While the game does not force the player to solve the story in a fixed sequence of steps, but instead allows free wondering through Hispaniola and Mexico, the main plot is still fairly linear. However it's how you'll handle that plot, where the devil lies. Will you be humane or genocidal? Treacherous or fair? The game neither rewards nor punishes either style of gameplay. It is up to you to decide whether you will murder a native village or trade with it, and your "dirty dozen" squad of conquistadors will have different opinion on your actions, resulting in their morale going up and down. And should it go down too much, you could end up with a rebellion on your hands...
But it's the tactical turn-based combat where the game really shines. Many complain it's too hard or too arbitrary, but I wholeheartedly disagree with them. It's a bit like a chess game with figures that don't always do exactly what you want them to, except it's entirely different. :)
When it's your turn you can select any one of your troopers and tell them where to go and who to attack. When you've moved all, the enemy gets to do the same. Not unlike XCOM, only done better in my opinion. Cover matters, positioning matters, outfitting your troopers with weapon and armour improvements matter, perks matter, battlefield traps and barricades matter, who to attack first and why matters. And pulling off a good defence or difficult attack is really satisfying and makes you feel good about yourself.
I am a typical save-scummer and will never click the "Iron man" campaign selection. I will replay the same battle many times in order to try out different tactical outcomes and combinations. But my aim isn't to save-scum to win the game as effectively as possible, but to extend the game as long as possible while getting the most enjoyable fights out of it. I finished the campaign once, then started it again, then just finished the first part of the game, then restarted it again, wanting to do some quests and battles from a different perspective, using different units and tactics.
The one shortcoming of the game, which is the main reason why I do this is, it's too short. The Hispaniola and Mexico campaigns combined, if you don't rush them, will give you some 30-40 hours of fun. An additional Inca campaign DLC would have been nice, but the devs said there's not gonna be one. A modding tool has been released which allows people to create additional plot twists and random events within the main campaigns, but I haven't seen anything available for download and play yet.
If you're into well thought out tactical games this one is for you.