Age of Wonders 3 (hereafter AoW3, because its too long to keep typing!) has a lot of the usual trapping of these sorts of games but with few nice additions and changes. You start by choosing your hero, a combination of fantasy race and fantasy archetype that will go onto define how your empire fights. The first dictates your starting city, with it's collection of build trees unique to each race, and the second a different upgrade path for units unique to each hero class. So for example, the Dreadnought gets a musketeers and some steampunky devices to build, but the Arch Druid gets elemental summons and the like. This means that your army will be a mix that will quickly become fairly unique to you.
The Core gameplay is pretty familar too; you build cities, and build up forces, to conquer or build more cities to build more forces to...you get the idea. There is a diplomacy engine, but to be honest it feels underdeveloped, and really only gives you the option to buy favours, although some independent cities will offer you quests to complete to "earn" their absorption into the Empire. Mostly though, this is a game of conquest, which shouldn't be surprising given the effort that has gone into the battle screens.
So, when you end up in a fight you have the choice of playing out the battle in a separate tactical, turn-based layer. This is nearly always worth doing if there is any doubt about victory, as un-expected casualties from the auto-resolve can be annoying and you can almost always do better doing it as the game clearly wants you to. The Battles play out on hex-maps complete with different terrain features and some environmental effects, and are generally fairly quick to get through. The "hard" stack limit of six units prevents them getting too big, although adjacent units to the fight can get sucked in for bigger engagements.
It does have a couple of quirks through. Firstly, for reasons I don't quite understand, damaged units stay at full effectiveness until dead, even though they are nicely modeled with differing numbers of little men in them as they stomp around. It feels like a missed opportunity for diversity between units that can be gradually ablated and the ones that are a single, all-or-nothing creature. Its also not always clear why a unit is less of more effective against others, something you often learn the hard way. This is where your hero tends to shine, however, levelling up, equipping loot, and gaining new powers from the global tech tree or from his own advancement.
The biggest weakness in the game though, comes through in the strategic layer, and that is the struggle in the endgame. You can "win" a match long before the game recognises it, and finishing off an opponents last few cities can be a brutal war of attrition to take out his cities. It's not like the Civ series, either, where you can just parcel these remnants off and go for the space or diplomatic victories. Maybe there is a trick to it, but I've not worked it out just yet.
All that said, I've sunk maybe thirty hours in AoW3 and I'm not quite done with it yet. It is a lot of fun, especially in its early- and mid-game, and has made a lot of effort to have variety and freshness on multiple play throughs. If you like these sorts of games, its well worth a look.