One contractor grade cardboard tube + a bit of time = nearly instant bookshelf.
From Kootoyoo: "I had originally purchased only 1 tube to make a toy box for the smallest...it kicked around the floor of the craft room for a while & I'd done nothing with it.All the while I'd been enjoying posts from this tumblr.
...then I got to thinking how they'd be wonderful as a bookshelf & that's what I've done. I've left the tubes natural & just given them a bit of a sand to remove the rough edge."
The compartments are held together by a bit of webbing. Go forth and create.