This is such a cost-effective and easy DIY project, and a great way to add a fun pattern to the bookcase. The supplies are enough 1/4″-thick foamcore to cover the open area of the shelves, enough fabric to cover the foam core, heavy-duty masking tape, scissors, a utility knife, measuring tape or ruler. First, measure the height and width of the shelves you want to cover, then cut the foamcore to fit. Make a few minor adjustment trims to make sure it would fit snugly into the shelves. Remember to allow a few millimeters of room for the fabric to cover the edges. Continue reading the tutorial in the source.