It is a stand alone game based on a fictional world where elves, orcs, humans, cat race called Khajiits are all normal populace. Add that to a land where breathtaking terrain filled with walking dead, dragons and others evils is available on your PC with almost a size to rival some MMOs. I put countless hours into this game and I have barely scratched it's surface.
By far, the best game I've seen in a 4+ years for anyone interested in that kind of environment or has an interest in old weapons.
Personally, I like to use the bow; nothing is more pleasing than nailing some moron at an extreme distance, silently and without using any magicka. It is too bad the damage output is so low, even with smithing, crafting and poison.
edit: The one thing I do not like about the game is the leveling system. It should be based on getting things accomplished, not repetition of skills. It reminds me of the macros I made when I used to play MMOs and learned skills (like Everquest); they aren't fun and don't serve any purpose other than being a time sink.