Library Shelves

I finished sorting my library books and now I ran out of shelf space.  There are not any extra shelves in the building.  So I either make another shelf like the one I have or I buy one.  Does anyone have suggestions as where to get shelving?  I need quite a bit as you can see all the boxes on the floor!

Here's a little reading nook between two shelves.  It's great for buddy reading.  I got these chairs from Walmart a few years back.