In the past i have played games in this genre (action rpg i guess)  but after playing them untill the end I realice that the history was horrible or missing at all.  
One of the main actractives in a game for me is the history, so I need your opinions to decide buy or not buy this game.
 

The Elder Scrolls games are very well known for their rich back stories. Though Oblivion is not the best in the series for the mass amount of side information about the game world you can find, it has tons, TONS more then the average game.

The main plot can get a tad boring when you have to close Oblivion gates, but other than that the story is very nice. Not to mention all the smaller stories from sub quests and so on, some of them are actually much better.

This game does has a great history. 
 
I'm sorry I had to, but yeah it does I loved Oblivion and after I was done I went around reading those stupid books.

It's very deep in story. You can even find books all over which can be pretty darn lengthy. There's plenty of history and backstory in the world of Tamriel, though unfortunately I found most of it to be pretty uninteresting, just like the game! Hey!

Oblivion has a hell of a lot of back story there if you want to explore it. You also might want to check out Fallout 3 and Dragon Age if that's the sort of thing that you're into.