New order

Dilemma: there are books everywhere. EVERYWHERE. 
I know, lucky me :) So how do I organise +-800 books across seven bookcases in different rooms in my house? 
Alphabetically yes, but that's not enough. Fiction, non-fiction, creative non-fiction. Classics, poetry, art, philosophy, biography, music, aviation, travel, reference. Journals, periodicals, coffee table books, children's books, miniature books.
Then there's shelf size to consider. One bookcase might perfectly house poetry, for example, but what happens when a volume doesn't fit on the shelf in which it is alphabetically required to reside? Does one start an A-Z shelf just for the big books?
And aesthetics. The books in my loungeroom are, for the sake of form over function, arranged in blocks of colour. (Which to a purist would be akin to filing a Mills & Boon in between Madame Bovary and Tess of the D'Urbervilles. Horrors!) Clearly, an alphabetised system will mess with my interior design palette - although I'm prepared to concede on this particular point.
But you can see from the images above (courtesy of Bookshelf Porn) how form is vital to function when it comes to books and decorating. Cool huh!...perhaps I should experiment with some book art at home.
How do you organise your books? Does anyone have an ingenious system that I need to know about??