How can I make a bookshelf using simple materials and tools?

To make a bookshelf using simple materials and tools, you can use wooden planks, screws, a drill, and a level. Cut the planks to the desired size for the shelves and sides of the bookshelf. Assemble the pieces by screwing them together, making sure to use the level to ensure the shelves are straight. Add additional support if needed. Sand the edges for a smooth finish, and then paint or stain the bookshelf as desired.