Personal libraries are for show-offs.
I don't need them. I don't need to show off my collection of books. I'm a book lover, so I don't need silly shelves taking up space in my room just because I may not remember where my books are, oh no. Book shelves are for losers who buy books by the color of their spines (so that the color goes well with the wallpaper) or insecure pretentious twats who believe that displaying all the books recommended by Oprah, New York Times, and whatever that they have and will never read will let people believe that they are intellectuals. Hah!
Why waste space in the house for shelves when you can fit more books by lining them up from wall to ceiling? You can also stash them under the couches and chairs (this is especially useful when your sofa is missing a leg or two), tables, and other crannies. And when you put all those mothballs around to ward off those annoying book-eating bugs, you are also making your house smell nice so you save money on those silly air-freshener nonsense. Besides there are always plenty of room in the extra bathroom that can be used as a book storeroom. In fact, using the family car to keep the books is the best move for the family - now everyone is forced to walk and we are all becoming trim and healthy AND we don't waste money on gas PLUS we are helping the environment become better.
Also, having the complete collection of Outlander, The Wheels of Time, Harry Potter and Lord Of The Rings books under the bed does wonder when some loser breaks into your room bent on theft, molest, or worse. Nothing like 28,991,443 pages, encased in sturdy hardcover binding, flung at that fiend's head to make your home safe and secure again.
If you want to waste money killing trees to make wimpy bookcases to show off your hoity-toity "intellectualism", go ahead. Wimp. Real readers need no personal libraries!