how do you want them to look? take crates from michaels, pile them on top of each other.
take cinder blocks/boards.
I used shelving board for frame and shelves with luan on the back, you can also use regular plywood. I cut the boards then glued with wood glue as well as secured with finishing nails. Once the glue was dry, I cleaned it up then primed & painted.
Hi Lo: Here's a site that may help: https://www.wikihow.com/Build-Wooden-Bookshelves
Good luck and happy hammering :)