Imagine you are looking through the eyes of another person who comes to visit your home or residence. As they walk through the front door, what do they see first? Clutter and overwhelming amounts of items can be intimidating to your guests. Studies even have shown that people who keep neat and tidy homes actually have lower stress levels which directly lead to lowered blood pressure.
You don’t always have to have an item in every single place. Open is not a bad thing, space wise. Imagine a bookcase. Your bookcase could look cluttered with every little nook and cranny filled with items other than books. Avoid bookshelves with clutter like the following picture:
Try to keep only books in your bookcase (bookends are of course allowed, too). It will look neater to any potential guests than having cluttered items elsewhere on the shelves.
Plus, again, empty space on your shelves is not a bad thing. Look at the empty space as more books for you to buy in the future and plan for that day when your bookshelves are full of what it was built to hold: books.