I think it was pretty inconsiderate of the person to bother someone whom is clearly busy, especially if it needs concentration like reading. It was polite of you to nicely tell him that you were busy. He could have gone and spoken to someone else. I think it was rude of him to continue talking to you, and that he was the one that was being impolite. A lot of people are like that though, but I wouldn't really bother with that.