How do you organize your books?

[Poiuyt]

I am in the process of building a new library in my home. What I am wondering about specifically is if you shelve your fiction paperbacks with hardcover books or if you keep them separate? Putting them altogether in alphabetical order makes the most sense as far as finding books easily, but shelving the paperbacks separately would be a more efficient use of space.

What about keeping to-be-read books separately? I tend to pick out my next book according to the mood I'm in, so it would be nice to have all those together.

Non-fiction I organize by subject without regard to the binding.