One of my high school friends kept all of her paperbacks (about 300 books) piled up against a wall in her room. She did a grid of books stacked horizontally and vertically. She said she had to play around with how things were stacked, but (and I really really wish I'd been able to figure this out when I examined the stack) had gotten it to the point that there were only a few keystone books she couldn't take out without tumbling things. That is, she could take out all the rest of the books.
Anyway, taking the books from the boxes and stacking them could work if you have wall space. Actually, if you ever get a hold of cheap wood, see if there are some hardcovers in your collection you probably won't want to reread any time soon and use them instead of cinder blocks.
(And, of course, if there are any you like anymore, maybe you could sell them to get money for the wood. )