How do I build a simple bookshelf?

See if these help you out Jeanie!

https://youtu.be/vH9EUTvA5tA

https://youtu.be/ZktBkPOVvd0

https://www.familyhandyman.com/woodworking/bookcase/simple-bookcase-plans/

the very simplest would be a board with two angle iron (Hardware store, home depot) fasten brackets onto shelf, fasten brackets to wall. These are not book shelves but they could be. I made the wine glass ones, these have iron strips (hardware store, home depot) and you buy brackets to fit into them. Very easy and very flexible. Our house is full of bookcases. . . (I have four in my room) it is easy to find bookcases at yard sales, Good will, etc. Some though we had made, some we made ourselves. A bookcase is really just two side pieces that have shelves fastened inside them. Sometimes the shelves can be adjustable, sometimes not.

Cheap and simple is to use 8x8x8 cinder blocks and a 1x8 plank. It will cost about $10 for a two level shelf and set up in 5 minutes. There are many variations of blocks and planks. They can be stained or painted.

Do a Google and YouTube search for cinder block shelves.

I used shelving board, glued and nailed with small finishing nails. Then primed and painted. You can add plywood to the back for stability if you need it. You might if it is a large bookshelf.