How Do You Organize Your Library?

John Ottinger III @ Grasping for the Wind []: asks:
As an avid reader, you probably have scads and scads of books. How do you like to organize them? Category, title, author, ebooks only, or some mix thereof? Explain your organizational system for books, (or lack of it) and why it works for you.

Organization? What is this word of which you speak?
Seriously, I have too many books to really organize them well, given space limitations. This has been doubly true since moving in with My Friends the Olsons.
I do roughly classify and store them as follows:
Fiction: This is almost exclusively science fiction and fantasy, or stuff that is very close to it (e.g. Jorge Luis Borges, Lewis Carroll).
Roleplaying books: I have plenty of these, ranging from a first edition D&D DMG to the latest stuff from Evil Hat, Chad Underkoffler, and the Forge.
“Reference books”: This is what I call non fiction that I like to dip in, and use ideas for games and writing and whatnot. Historical atlases, history books, a tarot book, a dictionary or two on mythology, and more. I also think of this as “browsing reading”, stuff to be gleaned and glanced over at my leisure.