I saw a fabulous post over at quilt while you're ahead. Monica, another book lover, has given up a meticulous system of book organisation and sorted her books by colour. The effect is beautiful. I would love to be so brave. In our house we have organised the books by subject and/or author. The system and it's in-built idiosyncrasies have evolved over fourteen years of marriage and three house moves.
PS - I will show him the second photo as evidence that he doesn't always put the books where they should be. I mean to say The Spanish Civil War smack in the middle of American political autobiographies tsk tsk.