How a slatted frame can be dozens of bookshelfs

raw material for the shelf
raw material for the shelf
a place for the shelf
the shelf

As you can see from the pictures, the idea is quite simple: Using two pieces of wood to rest the books on and two angles to rest the wood on. Since the books are usually bigger than the gap between the two bars there is no need for a massive board.

Oh and yes, all the materials (wall plugs too!) are from my favorite hardware store – „Sperrmüll“ (German for ‚bulky waste‘).