It's Batman Arkham Asylum in Mordor. If you cared about story I'll just sum it up: you died, an amnesiac elven spirit possess you - granting power for vengeance. Any more than that is spoiler. It has the hallmark of Batman game right down to the simple stealth mechanics, combat combos and take-downs. The major difference between this and Batman AA is the difficulty. It's toned down emphasize more on fun rather than difficulty.
There are no instant assault rifle kills if you get spotted, for example. Healing is a simple matter of finding that herb icon in the wilds. Escaping is not even hard. In fact, the only times I died is when I got over-confident and thought I could keep hacking at the endless hordes of orcs. Yes, I did say hordes. They come in smaller groups out there, but when you engage them in their stronghold, prepare for endless swarms if you let them raise the alert.
The whole Arkham Asylum Stealth/Combat is blended with Assassin Creed's open-world collectible/mini-mission stuff. And once again, the emphasis is on fun, not challenge. Though difficult spikes do exist in terms of high-swarm mobs (ghuls) or high damage big monster (caragors/graug). But once you pick up the basics (or upgrade the appropriate skill), you won't have much of a trouble dealing with it.
There is also the 'Orc Army Leaders' aspect that plays a part in the main campaign. From simple assassinations (you will fuck up the stealth somehow and trigger horde spawns), you will eventually be given a chance to dominate a ranking officer. This involves taking them down to low health and use a special ability to dominate. Once done, you can command them to assist in taking out other Orc Leaders. A randomly generated 'power struggle' mission will then appear to offer you an opportunity to kill the target and in the case of higher ranking chiefs, usurp them with your minion. The mission could be a Duel, Betrayal, or even your jackass minion getting captured and put out for public Execution, it's up to you to save his ass and kill his executioner.
Pictured: How demotions work in game.
There is also the much-praised Nemesis system in game where the orcs will remember you if they have defeated you or retreated from you. It's not a big deal, but it's nice to see a badly wounded orc you let escape earlier return with an eye-patch yammering about how he'll get you this time, Gadget - till you do an eight hit combo and chain two execution moves to shut him up. Also, if you let them beat you, they gain Power Rating which translates into additional combat bonuses etc.
Speaking of combat bonuses, the Orc leaders do have special properties that are hidden at first. You can uncover their Strengths/Weaknesses by interrogating Orc informants. This is helpful, because uncovering that this Super Strong Asshole Capable of Tearing Your Asshole 20 cm Bigger has a phobia for Caragors (Mordor rideable wolves) make them a piece of cake. Or the pesky Archer Chiefs that gets one-hit killed when taken down from stealth. It also helps knowing if one is Stealth-takedown immune before trying it. Heheh.
Overall, I highly recommend it - It's fun. But it does get old past the tenth hour or so. I got tired once I'm done with the first map and just powered through the second map. There's a high frequency of QTE too, so never let go of your keyboard and mouse and you should be okay.
A small tidbit: if you have Steam friend list and your friends die to those named orcs, you get Vendetta missions to avenge them.