How do you teach your children on being humble and modest?

DS (4.5 years old) is an early reader. He was reading since he was 3 or so. I think he has gotten way too much compliment from us and the teachers, now I am noticing something interesting. We were at a storytelling session today and the story lady was about to read storybooks to the kids. Each time she takes out a book, DS would read ALOUD each and every one of the book titles. Later today, we were at a Christmas symphony concert with a friend. They were about to play Nutcracker. DS and his buddy (same age) started arguing about who likes the nutcracker music more. DS said, "how would you like it more than me? You haven't even listened to the Nutcracker music before."

That "show off" / bragging behavior really bugs me. We talked about it tonight. I asked him why does he read out all the book titles aloud every time he sees one. He said it's because not every kid can read. Sigh. We then had a long talk about how it is important to be humble and modest. How bragging and showing off is going to make others feel sad, and eventually they would not want to be around him. People usually like to hang out with other people who makes them feel good and happy, not make them feel bad.

DS asked, what is modest? What is humble? I don't think he even know what I am talking about. I said we'll have to buy some books and read about it.

Has this happened to you and what did you do about it? Any good book you'd recommend?