How do you organize your books?

I see so many amazing pictures online of organized bookcases and bookshelves of books organize by series, genre, author, etc. (like the picture below). It makes me wish I could organize my books but I have too many to do anything.

I usually just organize my books based on whatever space I can find on a shelf. And for quite some time, I've been completely out of shelf space so that I've been storing my books in boxes or containers. At some point, I'm going to have to find some space for another bookcase but until then I'm going to keep my books as organized as I can in various boxes and containers.