Book shelves: either they're all empty or you haven't got enough, that's Murphy's Law.
Super good shelves can be quickly assembled with 1 x 12 shelving, obtainable in different lengths, and 12” x 12” x 4” ornamental concrete dividers, available in numerous designs; common around ground level patios so you can sneak a peek at a tea party.
Ideal for a recreation room or if you're renting, then it's easily dismantled and moved.
If you are going to store three-hole binders, they are 11 and 5/8, the same height as the blocks. Too tight a fit! Get what you need of wooden baseboard, ½” thick or something thicker for more clearance, and 11 inches long, width not too important, to place on top of the blocks to raise the shelf.
You can stack these four feet high. Remember one shelf, two blocks. Two shelves, four blocks. Have fun girls; surprise the old man when he come home!