A great way to learn about how different people think is to organize your books by Library of Congress Classification. I did this over the past weekend and had some interesting and surprising moments. I sorted everything into the letters that indicate the subject area (A, B, etc.) using the cataloging information recorded inside the book. I still have a big stack that I need to go back to that was "in-cataloging" at the time of publication. I am hoping they have sorted those out by now!
Once you get going, you can make some pretty good guesses about what is what. I could identify a "Q" very quickly, but was often wrong about the "T"s. Some of the categories (mostly B, and H) reflect the way that I had previously grouped my books. Other subject areas (T, E, R) grouped my books in new and different ways.
Books that used to be right near each other on the shelf are suddenly distant, and I think this comes down to the mind of the cataloger. For example, why is "My Tiny Life" by Julian Dibbell an "H", but "Play Money" (also by Dibbell) a "Q"? And if they are really quite different, why did "Play Money" make it to "Q" and not to "G", where the rest of my game books are?
Most of my graphic novel and comic material sorts under "P", which is where you expect to find the literature and language material. You can tell where my bias was: I would have sorted them all under "N" for finel art!