I have...let's see...three bookcases in my bedroom, four in my wee sitting room, and another at the top of the stairs. Books 'on the shelf' are generally those that I'm most likely to want to read, plus those of authors who are still alive and writing.
Then I have two ottomans, also filled with books, one with mostly kids books.
Then I have the...hang on a sec...12 at least, boxes in the attic-space off my bedroom. These are almost organised, I can put my hand to most books if I'm looking for them, though single-book authors are a pain to find. It's always a sad day when an author is relegated from 'the shelf' to 'the box', but sometimes I just plain run out of space.
In the bookcases themselves, any series is arranged in order, though the authors aren't in alphabetical order, more 'however I can get them to fit best'. Plus the two tall bookcases in the sitting room have my "early 20th century crime fiction collection"...except for the ones that ended up in boxes for lack of space!