Princess Lilue

Saw this question posted on this link BTT :

How do you arrange your books on your shelves? Is it by author, by genre, or you just put it where it falls on?

I just managed to splurge on a new book case yesterday, which i'm so totally in love with.. somehow, vivencia (or i suppose in the states you'd know them as 'pottery barn') always seems to have the exact furniture that i'd be dreaming of (& some which i didnt know that i'd want..hehe) that i just cant imagine getting it elsewhere. Well, i could, for a cheaper price no doubt, but much much less quality.

Anyway, at the moment, my books are pretty much all over the house. By my bedside, in boxes & some DIY shelves right next to the tv. I dont normally organise my books in any particular order, usually it'd go by sizes rather than author. Saw this website showing samples of rainbow bookshelves, but i doubt i have enough of similar coloured book to build one convincing-looking rainbow bookshelves.. haha..

So any suggestions before i start re-organising my books ?