I pretty much run out of space for my books, so I started this precarrious wall o'books that is starting to take over my room.
If you happen to have a comic book store in your area you will find that the cardboard (very very durable) boxes used to hold comics are excellent for storing regular sized paperbacks. I think I pay about $6 a box but I do get them discounted. Hope this helps.
I will keep the tip in mind
I've found building a little book castle and putting an armchair or a cushion in the middle is a great solution. You can pull a book out of the castle (carefully, like Jenga...) and sit in the middle and read it.
Pretty soon that is what it will come to, hahaha I use to call my fortress book jenga, becasue I keep seeing how high I can stack it before it all topples over