The worst thing you can do is buy substandard shelves. Sagging is a big risk to your shelves and your books. If hardcovers are your thing, or if you just have a lot of books, make sure you get pretty thick shelves. The wider your shelf is, the thicker the shelves should be. A great tip is to get a bookshelf with adjustable shelves. This allows you to put your taller, heavier hardcovers near the bottom and your soft covers near the top to balance the weight. You can also pick up some bookends to leave space on your shelves for personal items. The most popular things to put on the shelves, other than books, are antiques from around the world or personal leather journals. A globe would also be fitting. Anything that is either very personal or evokes a spirit of learning or culture.
You might also invest in a step stool or small ladder to reach your higher books. If you want to add an elegant or whimsical look, a rolling ladder would be perfect. You will have to attach a rod to your shelves though for the ladder to glide on, but this will allow you to move it easily along your shelves.
What else will you use the room for. Is this room serving as a study? Is it a place for work or reflection? Does it serve multiple purposes? If you have come this far you might consider investing in a high end desk if this is office space. Otherwise, a few leather armchairs and some understated tables would do nicely. Remember to have plenty of light in the room or no one will do much reading at all. A study table in one corner or near a window will allow guests to use your library, or you can use that area for pleasure reading away from your desk.
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