You could be forgiven for calling this game Arkham: Middle Earth. It has so much in common with Rocksteady's Batman games that you would swear that protagonist Talion is a distant relative of Bruce Wayne. The combat controls are virtually identical, the map looks suspiciously similiar, orcs that you can interrogate for special information are marked in green like the Riddler's goons, and you can even enter the spirit world to find clues and spot enemies through walls, very much like Batman's "detective vision"! I don't say this as a criticism but only because the similarities are impossible to ignore. But you know what? It works. This is a fun and compelling game, and it's always a treat to play in J.R.R. Tolkien's universe (although the look and feel of this game is definitely more influenced by the Peter Jackson films than Tolkien's novels, a fact that may bother purists, but would a purist even be playing this game in the first place?).
You as play Talion, a Ranger captain who lives and works near Mordor's Black Gate at a period set some time between The Hobbit and The Fellowship of the Ring, but when his family is killed by Sauron's minions, he somehow finds himself cursed with the inability to die, or rather the inability to stay dead, and so he sets out to seek revenge. The story is told through a series of rather excellent cutscenes featuring terrific animation and top-notch voice acting. And even though the story is standard fare for a video game (it's no Tolkien, I'll say that much), I actually found myself drawn to the central protagonist simply because of the high-quality of the cutscenes. It's a pity that there's no apparent way to rewatch them without playing the whole game from the beginning.
I would describe this as an emergent action game. It's open-world in the sense that you're free to go wherever you want whenever you want, and you can complete quests in the order of your choosing, but there are really no significant choices to be made, and despite the nice scenery, there's no sense of exploration and discovery, either. Everything is clearly marked on your map, and highlighting a point of interest gives you a marker that guides you to your destination. Furthermore, individual locations are fairly generic, and I think you'd be hard-pressed to get around the gameworld on your own without the markers to guide you since one area of the map looks very much like any other area. Even after 30+ hours of play, I never developed the sense of familiarity with the setting like I did in any of Bethesda's open-world games, or even the Borderland series. Shadow of Mordor is not the sort of game where you discover secrets or happen across a new vista.
But that's not to say the game itself is not compelling and fun. The free-form combat is very smooth and engaging with great animations, although the kill moves are quite brutal (the M rating is well-deserved), and you have a wide variety of maneuvers to help you dispatch your foes. You can even mount certain wild beasts and fight from their backs. It can be a lot of fun wandering into a band of twenty orcs and emerging without a scratch, although this does take some practice. As you complete missions and murder orcs, you will gain skill points that can be used to unlock new abilities for Talion, but it's pretty straightforward, and you'll easily have every skill and special ability available to you by the end of the game. You can also collect special runes from dispatched orc captains to add to your weapons (a sword, a dagger, and a bow) that introduces a level of customization to your character. Talion is a nimble fellow, too, and can scale virtually any cliff or wall he encounters, a useful ability when he wishes to remain unseen, and he can use certain parts of the environment to his advantage, like upsetting a nest of morgai flies to scatter his foes and make it easier to reach an objective without raising the alarm.
I think what really sets Shadow of Mordor apart from the crowd is its nemesis system which is almost a game in and of itself. The world is populated by a couple dozen persistent orc captains and warchiefs who represent your greatest combat challenges. If one of them kills you, or if he successfully flees from you in combat, he will increase in power and be harder to kill the next time, so you have to consider whether or not engaging a captain is worth the risk since repeated failures could lead to creating a high-level orc who will be very difficult to put down. Furthermore, if a standard orc kills you, he will be immediately promoted, so the roster of captains is constantly evolving. To help even the odds, each captain has weaknesses that can be exploited, but you can only learn about these weaknesses by interrogating certain low-level orcs known as "worms" who are identified by a green icon. Sometimes a captain might be impossible to defeat without knowing his weaknesses, so interrogating worms is often essential for success. And it gets more complicated from there.
The orc captains have their own internal power struggles, and you will see them rise through the ranks by betraying each other, or hosting feasts and hunts to raise their standing. These events generally happen "off camera" while you're out on your adventures, but you can also interrupt them by activating procedurally generated mission markers that will give you the opportunity to kill the captains to keep the orcs in turmoil and weaken Sauron's army. You eventually gain the power to dominate an orc's mind so that he does your bidding, and a major part of the game revolves around turning the orc army against itself and helping your branded captains rise to the level of warchief.
Shadow of Mordor's visuals are very attractive with clean textures, realistic weather and time-of-day effects, and superb animations, so I have no complaints there. Performance in Linux is pretty good, and although benchmarks show that it lags behind Windows in terms of raw speed, I still found it smooth and responsive, so hats off to Feral Interactive for another fine port.
So bottom line, this is an enjoyable and well-made game that does exactly what the developers set out to do and will give you dozens of hours of entertainment romping through Tolkien's Middle Earth sandbox and murdering orcs. And I haven't even mentioned the volumes of canonical Middle Earth lore that Monolith managed to cram into this game.