At my new house, we just bought a bookshelf from someone in the neighborhood. The top two shelves are full of books, and the entire bottom half is filled with board games. Eventually I'd like to have two shelves for more space, but this one is fine for now. Of the books I do have, one shelf is devoted to series (Harry Potter, Hunger Games, Divergent, and Twilight, because yes, I went through that phase...) The top shelf has the more random books, not arranged in any particular order yet. I try to organize by author and by height when I'm really paying attention.
I do have a second bookshelf in the office with all of my academic books on it, but those just went up there today and are not very well organized yet. Eventually they'll be separated between clinical and school counseling and then by general topic. Slowly but surely getting there.