Unpredictable fun, if you like your fun unpredictable.
And for the record, "just right" doesn't really fit the difficulty; it's more like "in the middle".
Story:
The story comes from the movies. Anyone who's read the books should be able to keep up, those who have read the movies will know what's going on better than I did, and those who've done neither can mostly ignore the story and play the game, though it'll be a bit harder to keep track of everyone without a story to tell you who's who. Except for a few scenes from the Second Age (AKA the ancient past), the game follows the story of the Lord of the Rings movies, modified to fit a turn-based strategy game, meaning that, depending on your skill, Boromir might not die at all, or might die several times.
Gameplay:
Though some RPG elements come into play, specifically EXP and a shop system, this game is first and foremost a turn-based strategy game, in the vein of Fire Emblem. Despite what the opening video and title screen might show, the armies will never reach massive levels, at most battles of 30 vs. 40 or so are seen, and it gets as low as 3 vs. 7. Of course, the player is (almost) always the smaller number.
When you start your game you choose from one of six commanders, three on the side of good and three on the side of evil. The game has two save slots, one for either side, meaning that you might want to play a few of the first maps with each commander before settling on the two you want. Then, you pick from 30 maps, of which you start with only three, including the two tutorials, based upon the Lord of the Rings movie trilogy. Journeying through the various maps you (usually) choose from among seven or eight heroes to accompany your commander into battle, placing these characters on pre-determined spaces on each map. Every other unit, including all enemy commanders/heroes, is already set in place, for the sake of the specific fight. You're given the mission goals and a bit of strategy before you head in, but you can't actually see the maps without starting to play them, and there will likely be times when you quit at the start to change your heroes to ones who better fit the map. As stated, the game is turn-based, and for the most part the side that goes first depends upon the map, though a few battles will always have your side go first. Both sides have the same 30 maps, but the units change depending on the side you're on, and they're rarely changed in your favor (typically a few units are added or subtracted from one side or the other).
At the start of every turn, you get Command Points (CP) based on your heroes' maximum/minimum CP numbers, which range from Ugluk's 0-2 a turn to Saruman's 1-5 a turn. The number is decided randomly, and it typically seems to favor the computer's side. For every command point in a flank (there are three flanks total in every map but one) the player (human or AI) can move one unit on that flank, unless determined by the random pre-turn event. These events include the most common "free move" granting an extra move on the flank of the player's choice, to "rally" letting them move all (up to eight, actually) units on a flank, to "disorder" nullifying all command points granted on a turn to a given flank. Again, these are random, but seem to favor the AI player.
As for actually moving units, that's simple enough, once you learn who can move how much, attack from how far away, and deal what damage. And the damage factor is a complicated equation all its own. Instead of a unit dealing what their attack stat says they'll deal, a unit will deal somewhere between none of and twice their attack stat, and the higher the stat actually is, the less of a chance of actually dealing those two extremes. I'd give examples, but the exact formula is best left for a FAQ.
There are a few last gameplay elements, both that have random aspects. First off, projectiles, specifically whether they hit or miss. Most evident in catapults and the like, which claim a 50% chance of missing, but seem to hit more for the computer than for the human's side. Other projectiles (arrows, Gimli's throwing axes, boulders, etc.) have a much smaller failure margin, but it still can occur. Finally, there's morale, a stat that varies from "fearless" to "cowardly". Weaker morale characters have a greater chance of running off when you attack them, and characters who run off can't do anything next turn, as well as leaving the battlefield by a number of spaces (not always a bad thing though). Morale actually tends to work in the player's favor, stunning the enemy just when they need it to. But all in all, there's a fair bit of chance involved, and a victory is (almost) never assured 100%.
Besides all that, there's not much left to the game. As stated above, heroes can gain EXP, but don't level-up with it, it's instead spent at a "shop" type place unique to every character, though the upgrades bought are always the same, and end with the character purchasing them at the same level (in the end at least) no matter how many times the game is played. Skills and items are also available; the latter can be consumed once before requiring purchase at the store again (and can only be bought out of battle, though sometimes when a hero is the one to make a kill they'll get an item as a reward), while the former almost always last just a turn, giving bonuses that include offense increase, more command points, or extra movement. Some powers are minor boosts that give a character the advantage in a single fight, while others affect the entire flank and can change the tide of a battle. However, all skills cost SP (Spirit Points, AKA Magic Points), which is gained automatically every turn, and fairly slowly at that. Don't expect to spam projectile immunity or morale penalty every turn unless there are at least three heroes not doing anything with their powers. And, as might be expected, a few powers also have the randomness factor, mainly those that deal damage to enemy units.
Difficulty:
Seriously, the game's not very hard. The AI can be somewhat stupid, and the "difficultly level" only increases enemy power (increasing the HP and offense of all enemy units), not the intelligence level itself. The randomness level is what makes it difficult though, sometimes the player can breeze through, and sometimes they'll hit a wall. Typically a victory can be pulled off, once the player figures what they're doing.
Multiplayer:
Multiplayer linking is available, allowing two people to play turn-by-turn multiplayer, and unlock a bonus (and fairly difficult) map. "Hotseat" multiplayer is also available, allowing someone to pass their GBA to a friend and back again (which is a lot less awkward then is sounds), though you can't get the map this way. In addition, most of the maps are changed again, this time to try and balance them out to make things "fair."
Graphics and Sound:
The graphics are okay, nothing special. Character animations are limited in the fight sequences, which can be skipped, once ability to do so in unlocked by beating the game, and outside of those the game has a top-down view that's passable. The battlefields themselves look quite good, but that's actually a drawback for gameplay, telling apart rough ground from smooth ground (rough hinders movement and adds defense, sometimes) can be a challenge. The top corners are nice enough to say what type of ground the cursor is on, so long as there's no unit there already, in which case it shows the unit's face instead. In addition, walls sometimes block line of fire and sometimes don't, it's almost impossible to tell, for a human. The computer on the other hand is perfectly aware of terrain details, knowing where it can hide from catapults and the like. Yet again, the AI gets the advantage.
Sound and music are taken from the movies, and again, not bad. The music is good, but it's all the battle music, with the result that there are only about five to seven themes, two of which get played far too often. There are also movement sound effects, but they're inconsistent, not always occurring when a unit is selected. A few other sound effects occur regularly, but they're nothing to really take note of.
Replay Value:
First off, beating the game on the other side of morality, which tends to unlock a few extra maps, heroes, and the like depending on your difficulty level. It also changes gameplay style greatly, as the good side focuses more on defensive missions that typically involve protecting something, or just staying alive, while evil tends to get killing missions that require charging out into the battlefield to finish off units. Both sides have both kinds of mission (typically opposite of each other, of course), but each kind is more noticeable on its given side. Besides that, there's the multiplayer, but with the random numbers of the rest of the game still there (though more balanced out since it's two humans against each other) it's less strategy and more of whoever gets more command points/heavy on various turns, just like in the main game, only with bragging rights on the line.
Game/code errors:
Important enough to get a section all their own. Basically, the number you see isn't always the number you get. For example, the Rohan Warrior claims a four attack, but it's really only a three, though the game's balanced as if it were a four. Any mission where you need to rely on Rohirrim Foot Soldiers gets a lot harder as a result. A couple of upgrades also aren't quite exact, and skills rarely have the numbers they claim (often being off by some percentage or the like), usually on the side of weaker than they should be. Basically, don't trust what the game says; trust how it acts when you play with it before deciding what works.
Overall:
It's a fairly fun game that lasts quite a while, but only if you can stand the battles and their lack of exact numbers found in various other strategy titles, or you just really want a fairly good Lord of the Rings strategy game. Otherwise, you're better off sticking with a game where a ten attack deals ten damage and 50% chance of missing is really 50%.
Scoring:
Storytelling: 6/10
Gameplay Quality: 7/10
Graphical Achievement: 6/10
Sound and Music: 7/10
Enjoyment Level: 8/10
Length and Replay Value: 8/10
Overall Score: 7.5/10 (Not an average)