banana "is a" fruit

You can never read too much about Object Oriented Programming and it's concepts. Once you got it you realize that it's a natural way of doing things. You'll never be satisfied with your level of understanding but that's also natural.
If you are a flasher then at some point down the road you'll see that in fact that's what you were doing all along. Even when using your mouse and drawing movie clips on stage. Because MovieClips are objects. In fact I think that Flash is a cool way to learn how to work with objects. It's also a cool way to learn how to do programming in the first place.
For those who are learning and not only for them another article on the subject can but only add value. So I want to recommend a good one here: Object-Oriented Concepts from nefariousdesigns. Be shure to check the js and php followups also.
Enjoy :)