Predictably, the game is short, sometimes broken, and generally not that much fun to play.
The game is basically a mixture of hack-and-slash, platforming, and dragon riding. The hack-and-slash aspect of the game extremely frustrating and repetitive, due in no small part to the horrendous fixed-position camera, which seems to be working against you most of the time. Rarely will the camera give you a decent view of the action. Instead, it seems content with hiding you behind enemies and objects, and certainly does an exceptional job of obscuring the path to the next screen, forcing you wander aimlessly and jump like a madman in every direction until you finally find the hidden hallway or ledge.
The actual combat is what you would expect, meaning that you just run around while mashing the two attack buttons until every enemy is defeated. The hit-detection is also conspiring against you, as you'll often see your sword pass right through an enemy, before getting slammed to the ground. There are a few attacks that can snap a guy out of an attack animation, and you'll most likely be spamming those attacks throughout the game.
Since Eragon is a Dragon Rider, you'll also be able to use magic against your enemies, but these aren't entertaining for very long. You'll be able to push and pull enemies, which is kind of cool the first couple of times, but gets old fast. You'll also get to imbue your arrows with magic, and even set an enemy on fire, but your mana takes forever to recharge after casting these spells, so you won't be using them as often as you would like. Besides attack spells, you also get some context-sensitive spells, but you feel more like you're hitting a generic "action" button than creatively using your magic to overcome various obstacles. Lastly, you occasionally get to summon your dragon to help you, but that ability is also context-sensitive, so it suffers from the same problem.
There are also some platforming elements, such as climbing up and down stuff, and grabbing onto ledges as you make your way across. These are completely boring and not entertaining in the slightest. To make matters worse, the game throws these ledges at you constantly, and half the time, you won't even be able to see them, thanks to the camera.
Where the game really shines is in the dragon riding levels, which can be quite fun. At this point, the game becomes a rail shooter, as you move your dragon, shoot exploding arrows, and breathe deadly fire on your enemies. The only problem is that you're essentially flying around in a circle, so you'll notice the level loop constantly as you take out the enemies, and then take them out again, since they respawned, and repeat the process until you either kill X enemies or simply die. The fire looks awesome, and it's always fun to kill hordes of enemies over and over again, watching as they make pathetic attempts to bring you down. What would make it really great would be some sort of leveling system.
Unfortunately, that's not the case. What you get is the same pretentious character development system that movie-based games often employ, where you receive fixed upgrades to your arsenal at the end of every level, that do not stick with you should you return to a previous level. This also makes killing enemies pointless (unless it's required), and eventually you'll just attempt to skip the fights entirely to make the game end faster.
There's also a co-op mode, that lets a second player take control of the CPU ally (or the dragon, in the aerial levels), but adding a second player to the mix only makes the camera angrier, since both players are needed to advance to the next screen. Occasionally you'll get lucky and the player left behind will simply teleport to the right location, but more often than not, one player will be stopped by an invisible wall, which will remain there until the other player catches up.
The storyline is weak, and only enforces the idea that you're just some random guy running around random environments killing random people who randomly want you dead. This did not surprise me in the least, but there was one particular moment that caught my attention. In one level, you run through an endless tower, and meet the bad guy, who, in one of the biggest Star Wars rip-offs I've ever seen, commands you to join him, before getting shot in the face by some guy who just happened to be in the right place at the right time.
The graphics themselves aren't nearly as bad as the game. While the character models look dry, the environment looks nice, the draw distance is never a problem, and the game manages to hold a steady frame rate throughout the adventure. On the audio side of the spectrum, the voice acting is passable, but the script is full of terrible puns and one-liners. It's especially bad in the first half of the game, where you're partnered with Brom. His suggestions to "use your magic again" are annoying, and so frequent that you'll soon wish you never had magic powers. The musical score is actually exceptional, and it does its best to keep you engaged, a feat that would have been accomplished, had the game not been so bad.
The main quest takes about 5-6 hours, and it's a good opportunity to earn some easy achievement points, but once you're done, it's unlikely that you'll ever return to this world. The dragon riding levels are fun, and the music is great, but in the end, the negatives definitely outweigh the positives. This game should not deserve a place in your collection, but if you're at all curious, you might as well give it a rent.