Info Source Categorizing

Have you ever tried looking through your library of books and categorize what information you have on hand through that filter in your mind? I mean, not just "math, history, literature," but also how they will help you and make you feel when you read them and stuff .... If you put 1) how it makes you feel/how or when you can use it and 2) what subject matter they are, you'll find an interesting matrix in your head. It's really kinda cool. And once that matrix is in place, you can make it more complex by putting dates in it ... like when you have used it, and when you project you can use it later according to your future plans. It makes for something like a 3D matrix.