This game is what you could call the "definitive" version of Disciples 3. It takes a lot from the first two iteration of D3 and revamps it to make something that is actually enjoyable to play.
The biggest problem with original D3 is that it tried to be as close as possible to Disciples 2 in some parts and something completely different (mostly a HoMM clone) in others. The result was an inconsistent, bipolar mess that was neither a proper successor to D2 nor a good rival to Heroes franchise. Not to mention buggy.
D3:Reincarnation tries to reconcile the two dysfunctional aspects of the earlier D3 games, and, in my opinion, succeeds in doing so.
For those who never played Disciples 3 before: this is turn-based strategy game in the vein of Heroes of Might and Magic. You start with a capital city and a hero, and your job is to recruit an army, explore the map, gather resources, capture new cities, level up yourself and your army, and eventually defeat whatever is the boss of that map particular map.
What sets this game apart from HoMM, Eador and similar games is the fact that your "army" consist of only a few characters (the actual number is determined by your hero's leadership skill, but caps at six), each of whom gains experience and levels up independently. For that reason it feels more like leading a party of characters in an RPG, than leading an army in a strategy game.
This impression is enforced even further by the inventory/equipment system for heroes.
Characters don't die permanently unless your entire army gets wiped and can be revived by potions, spells or by paying money in a controlled towns. After gaining three levels, a character "upgrades" to a more powerful class, granted you built the appropriate building in your capital. Some characters have mutually exclusive upgrade paths, allowing you to customize your army composition to better suit your play style.
When playing single player campaign, your hero retains the levels and equipment from the previous map, but the army starts from square one.
This version of D3 includes 4 playable factions and a campaign for each of them. Campaign themselves were redesigned from the earlier versions and now include water traveling. Character stats were also changed substantially to better fit the new hex-based combat (earlier versions just took the stats system from D2 and tried to make it work in a completely new combat system, with not so stellar results).
Overall, this version of D3 takes all that was good in previous versions and reworks the rest. If you have an interest in this genre, and weren't irreversibly scarred by earlier D3 versions, you should find this to be a very enjoyable game. It may not be Disciples 2, but I can wholeheartedly recommend it.