From where I'm sitting I can see 6 bookcases:
The first is under the TV. It's just a single, 4' long shelf, 18" high. It contains oversized, coffetable type books. I like to use these photos for artwork reference.
Moving to the right is the 3 shelf unit at the front door. The top shelf is basically empty. It has sides and a back where I drop off my keys and whatnots when I come home. The bottom 2 shelves are just slightly shorter than the first bookcase, so it also holds oversized books of a general catagory.
Then there's the 4 shelf unit that I can see sitting in the hallway. That's full of your basic sized hardcover nonfiction books. Mostly pertaining to budgeting (which I don't do), gardening (which I don't do) and cooking (which, surprise, I don't do).
Past that doorway and back into this room is the 7 shelf unit behind the couch. The top shelf is shorter and full of mass market books. The next five shelves are the perfect height for basic hardcover and trade paperbacks. These are all "readables". Novels, biographies, medical narratives...The bottom shelf is tall and holds more oversized books, again, mostly art reference.
Behind me is a built-in desk unit with 12" wide shelving on each side. These contain the same types of books that are in the hallway, but in paperback.
Now we head up to the ceiling! I have shelving above all the doors and windows which hold mass market books that I got about 25-30 years ago when I worked at B. Dalton. Back then we were allowed to take stripped books home. So I would take a copy of just about anything we were stripping, thinking one day I would retire and have a chance to read them. Don't know if that's ever going to happen now but I still have the books!
Aren't you glad you asked?